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Re: [Losmandy_users] Re: Polar Alignment / Guiding Tracking


Feb 19 5:57 PM

 


----------------------------

#41822 Feb 19 5:57 PM

Hi,



Couple of quesitons to the Guru's out there...



1. How close do people generally get their polar alignment in permanent installations? I'm in the process of setting up a pier and can plonk the mount on and be within ~7' of the pole - is that reasonable, or should I spend more time trying to hone in closer? When adding more stars to the model it seems that the error jumps around by a few mninutes, so will I end up chasing my tail?



I've previously tried using the Gemini polar alignment tools with varied success - it seems hit or miss whether you end up closer or not.



2. When auto guiding, do people generally have the mount set for Siderial or Adaptive King?



3. Is if odd that when using Siderial and doing a series of alignments I get a reported polar alignment error of ~ 7' on each axis, but when I do a number of alignments when set to Adaptive King I get a reported polar alignment error of 30+' in each axis? I didn't touch the alt or az between alignments. Should I align on Siderial and then switch to Adaptive King?



I'm sure I'll sort all this out in time, but I'd be interested to know if anyone has the answers.



Cheers & thanks,

Rod





Make Yahoo!7 your homepage and win a trip to the Quiksilver Pro. Find out more



----------------------------

#41825 Feb 19 6:49 PM

Hi Rod,



1. I usually get my polar alignment to less than 1 arcminute in both

axis. You can do this too, since you have a permanent setup. I'd

suggest using drift alignment or PemPro 2 to help you do this. Gemini

polar correction function is good, but the results can vary.



2. I usually autoguide set to Sidereal rate. I almost never shoot

below 30 degrees above the horizon, so Adaptive King wouldn't be very

useful anyway.



3. That is strange! I've never tried to build a model when set to

Adaptive King rate. Perhaps the extra rate changes involved in this

mode interfere with building the model? Don't know.



Regards,



-Paul



--- In Losmandy_users@yahoogroups.com, Rod Mckay rodnscope@...>

wrote: >

>

> Hi,

>

> Couple of quesitons to the Guru's out there...

>

> 1. How close do people generally get their polar alignment in

permanent installations? I'm in the process of setting up a pier and

can plonk the mount on and be within ~7' of the pole - is that

reasonable, or should I spend more time trying to hone in closer?

When adding more stars to the model it seems that the error jumps

around by a few mninutes, so will I end up chasing my tail? >

> I've previously tried using the Gemini polar alignment tools with

varied success - it seems hit or miss whether you end up closer or

not. >

> 2. When auto guiding, do people generally have the mount set for

Siderial or Adaptive King? >

> 3. Is if odd that when using Siderial and doing a series of

alignments I get a reported polar alignment error of ~ 7' on each

axis, but when I do a number of alignments when set to Adaptive King

I get a reported polar alignment error of 30+' in each axis? I

didn't touch the alt or az between alignments. Should I align on

Siderial and then switch to Adaptive King? >

> I'm sure I'll sort all this out in time, but I'd be interested to

know if anyone has the answers. >

> Cheers & thanks,

> Rod

>

>

> Make Yahoo!7 your homepage and win a trip to the Quiksilver

Pro. Find out more >



----------------------------

#41826 Feb 19 7:10 PM

First, I do not have a permanent mount. That's a year or two down the

road at least.



I use my polar scope to get close. For visual observing this is more

than enough. However, I do ccd quite a bit and recently purchased

Pempro to help evaluate the mount.



Pempro has a great Polar Alignment tool that can't be beat. It's a

drift alignment tool that will, after just 10 or 15 seconds of

observing, let you know how close you are. Then it will guide you

towards getting the alignment closer.



Results were nothing short of astounding, I was within 3 arc seconds

in each axis by the time I was done!



Tom P.





--- In Losmandy_users@yahoogroups.com, Rod Mckay rodnscope@...>

wrote: >

>

> Hi,

>

> Couple of quesitons to the Guru's out there...

>

> 1. How close do people generally get their polar alignment in

permanent installations? I'm in the process of setting up a pier and

can plonk the mount on and be within ~7' of the pole - is that

reasonable, or should I spend more time trying to hone in closer?

When adding more stars to the model it seems that the error jumps

around by a few mninutes, so will I end up chasing my tail? >

> I've previously tried using the Gemini polar alignment tools with

varied success - it seems hit or miss whether you end up closer or

not. >

> 2. When auto guiding, do people generally have the mount set for

Siderial or Adaptive King? >

> 3. Is if odd that when using Siderial and doing a series of

alignments I get a reported polar alignment error of ~ 7' on each

axis, but when I do a number of alignments when set to Adaptive King

I get a reported polar alignment error of 30+' in each axis? I

didn't touch the alt or az between alignments. Should I align on

Siderial and then switch to Adaptive King? >

> I'm sure I'll sort all this out in time, but I'd be interested to

know if anyone has the answers. >

> Cheers & thanks,

> Rod

>

>

> Make Yahoo!7 your homepage and win a trip to the Quiksilver

Pro. Find out more >







----------------------------

#41827 Feb 19 8:10 PM

Rod,



It's often a confusing issue, but the modeling (using lots of stars)

is for go-to slewing accuracy and not tracking.



If you want accurate tracking, you need to worry about polar

alignment. How close it needs to be depends on your imaging

requirements (how big your camera FOV is, how good your resolution,

how long single exposures will be, etc.) I suggest aligning as well

as you guess you need it to be, then do some test exposures and see if

you get field rotation in your shots. I think a lot of people sweat

about really precise polar alignment without needing to.



If you are guiding (i.e. using an autoguider or manually guiding the

old way with an eyepiece), then the tracking rate you choose doesn't

matter since the guiding will actively correct the mount's tracking.

So I just leave my mount set to sidereal tracking rate. The other

tracking rates, including lunar and solar) are most useful in cases

where you are *not* guiding like for visual use or say, photographing

a solar eclipse sequence.



It's interesting that you found some odd interaction between the King

rate and the mount modeling, but I think that's not important. Just

set it up using sidereal rate, then switch once you're done building

the model. And as I said earlier, if you're guiding, just leave the

mount in sidereal mode.



Dave Kodama



--- In Losmandy_users@yahoogroups.com, Rod Mckay rodnscope@...> wrote:

>

>

> Hi,

>

> Couple of quesitons to the Guru's out there...

>

> 1. How close do people generally get their polar alignment in

permanent installations? I'm in the process of setting up a pier and

can plonk the mount on and be within ~7' of the pole - is that

reasonable, or should I spend more time trying to hone in closer?

When adding more stars to the model it seems that the error jumps

around by a few mninutes, so will I end up chasing my tail?

>

> I've previously tried using the Gemini polar alignment tools with

varied success - it seems hit or miss whether you end up closer or not.

>

> 2. When auto guiding, do people generally have the mount set for

Siderial or Adaptive King?

>

> 3. Is if odd that when using Siderial and doing a series of

alignments I get a reported polar alignment error of ~ 7' on each

axis, but when I do a number of alignments when set to Adaptive King I

get a reported polar alignment error of 30+' in each axis? I didn't

touch the alt or az between alignments. Should I align on Siderial

and then switch to Adaptive King?

>

> I'm sure I'll sort all this out in time, but I'd be interested to

know if anyone has the answers.

>

> Cheers & thanks,

> Rod

>

>

> Make Yahoo!7 your homepage and win a trip to the Quiksilver

Pro. Find out more

>



----------------------------

#41828 Feb 19 9:51 PM

Actually Gemini has a tracking error compensation so the below is not strictly speaking

true. For shorter exposures, I'd guess five to ten minutes, a "kinda oK aligned scope" say

to within 15 arc minutes of the pole may not show that much field rotation to merit

zeroing in on the polar alignment.



Wiser heads than me may have some views on that. But basically once the tracking is

working with a polar aligment compensation the only remaining issue is field rotation.

While field rortation is a big deal if you are using an alt-az mount without a wedge, once

you have gotten "pretty durn close" to polar aligned and have drift correction (like Gemini)

I don't think there'd be much need for a precise polar alignment except on real long

exposure work.



maybe someone here can elaborate....



regards

Greg N

--- In Losmandy_users@yahoogroups.com, "Dave Kodama" kodama@...> wrote:

>

> Rod,

>

> It's often a confusing issue, but the modeling (using lots of stars)

> is for go-to slewing accuracy and not tracking.

>

> If you want accurate tracking, you need to worry about polar

> alignment. How close it needs to be depends on your imaging

> requirements (how big your camera FOV is, how good your resolution,

> how long single exposures will be, etc.) I suggest aligning as well

> as you guess you need it to be, then do some test exposures and see if

> you get field rotation in your shots. I think a lot of people sweat

> about really precise polar alignment without needing to.

>

> If you are guiding (i.e. using an autoguider or manually guiding the

> old way with an eyepiece), then the tracking rate you choose doesn't

> matter since the guiding will actively correct the mount's tracking.

> So I just leave my mount set to sidereal tracking rate. The other

> tracking rates, including lunar and solar) are most useful in cases

> where you are *not* guiding like for visual use or say, photographing

> a solar eclipse sequence.

>

> It's interesting that you found some odd interaction between the King

> rate and the mount modeling, but I think that's not important. Just

> set it up using sidereal rate, then switch once you're done building

> the model. And as I said earlier, if you're guiding, just leave the

> mount in sidereal mode.

>

> Dave Kodama

>

>

> --- In Losmandy_users@yahoogroups.com, Rod Mckay rodnscope@> wrote:

> >

> >

> > Hi,

> >

> > Couple of quesitons to the Guru's out there...

> >

> > 1. How close do people generally get their polar alignment in

> permanent installations? I'm in the process of setting up a pier and

> can plonk the mount on and be within ~7' of the pole - is that

> reasonable, or should I spend more time trying to hone in closer?

> When adding more stars to the model it seems that the error jumps

> around by a few mninutes, so will I end up chasing my tail?

> >

> > I've previously tried using the Gemini polar alignment tools with

> varied success - it seems hit or miss whether you end up closer or not.

> >

> > 2. When auto guiding, do people generally have the mount set for

> Siderial or Adaptive King?

> >

> > 3. Is if odd that when using Siderial and doing a series of

> alignments I get a reported polar alignment error of ~ 7' on each

> axis, but when I do a number of alignments when set to Adaptive King I

> get a reported polar alignment error of 30+' in each axis? I didn't

> touch the alt or az between alignments. Should I align on Siderial

> and then switch to Adaptive King?

> >

> > I'm sure I'll sort all this out in time, but I'd be interested to

> know if anyone has the answers.

> >

> > Cheers & thanks,

> > Rod

> >

> >

> > Make Yahoo!7 your homepage and win a trip to the Quiksilver

> Pro. Find out more

> >

>







----------------------------

#41829 Feb 19 10:24 PM

Greg,



Aside from tweaking the tracking rate constants or periodic error

correction which are RA-axis-only adjustments, I was not aware of any

kind of tracking compensation that is done based on computed polar

misalignment. For this to work, the mount would have to move in both

RA and DEC. Can you explain the tracking error compensation you're

referring to?



Dave



--- In Losmandy_users@yahoogroups.com, "gnowellsct" tim71pos@...> wrote:

>

> Actually Gemini has a tracking error compensation so the below is

not strictly speaking

> true. For shorter exposures, I'd guess five to ten minutes, a

"kinda oK aligned scope" say

> to within 15 arc minutes of the pole may not show that much field

rotation to merit

> zeroing in on the polar alignment.

>

> Wiser heads than me may have some views on that. But basically once

the tracking is

> working with a polar aligment compensation the only remaining issue

is field rotation.

> While field rortation is a big deal if you are using an alt-az mount

without a wedge, once

> you have gotten "pretty durn close" to polar aligned and have drift

correction (like Gemini)

> I don't think there'd be much need for a precise polar alignment

except on real long

> exposure work.

>

> maybe someone here can elaborate....

>

> regards

> Greg N

>

> --- In Losmandy_users@yahoogroups.com, "Dave Kodama" kodama@> wrote:

> >

> > Rod,

> >

> > It's often a confusing issue, but the modeling (using lots of stars)

> > is for go-to slewing accuracy and not tracking.

> >

> > If you want accurate tracking, you need to worry about polar

> > alignment. How close it needs to be depends on your imaging

> > requirements (how big your camera FOV is, how good your resolution,

> > how long single exposures will be, etc.) I suggest aligning as well

> > as you guess you need it to be, then do some test exposures and see if

> > you get field rotation in your shots. I think a lot of people sweat

> > about really precise polar alignment without needing to.

> >

> > If you are guiding (i.e. using an autoguider or manually guiding the

> > old way with an eyepiece), then the tracking rate you choose doesn't

> > matter since the guiding will actively correct the mount's tracking.

> > So I just leave my mount set to sidereal tracking rate. The other

> > tracking rates, including lunar and solar) are most useful in cases

> > where you are *not* guiding like for visual use or say, photographing

> > a solar eclipse sequence.

> >

> > It's interesting that you found some odd interaction between the King

> > rate and the mount modeling, but I think that's not important. Just

> > set it up using sidereal rate, then switch once you're done building

> > the model. And as I said earlier, if you're guiding, just leave the

> > mount in sidereal mode.

> >

> > Dave Kodama

> >

> >

> > --- In Losmandy_users@yahoogroups.com, Rod Mckay rodnscope@> wrote:

> > >

> > >

> > > Hi,

> > >

> > > Couple of quesitons to the Guru's out there...

> > >

> > > 1. How close do people generally get their polar alignment in

> > permanent installations? I'm in the process of setting up a pier and

> > can plonk the mount on and be within ~7' of the pole - is that

> > reasonable, or should I spend more time trying to hone in closer?

> > When adding more stars to the model it seems that the error jumps

> > around by a few mninutes, so will I end up chasing my tail?

> > >

> > > I've previously tried using the Gemini polar alignment tools with

> > varied success - it seems hit or miss whether you end up closer or

not.

> > >

> > > 2. When auto guiding, do people generally have the mount set for

> > Siderial or Adaptive King?

> > >

> > > 3. Is if odd that when using Siderial and doing a series of

> > alignments I get a reported polar alignment error of ~ 7' on each

> > axis, but when I do a number of alignments when set to Adaptive King I

> > get a reported polar alignment error of 30+' in each axis? I didn't

> > touch the alt or az between alignments. Should I align on Siderial

> > and then switch to Adaptive King?

> > >

> > > I'm sure I'll sort all this out in time, but I'd be interested to

> > know if anyone has the answers.

> > >

> > > Cheers & thanks,

> > > Rod

> > >

> > >

> > > Make Yahoo!7 your homepage and win a trip to the Quiksilver

> > Pro. Find out more

> > >

> >

>



----------------------------

#41831 Feb 19 11:55 PM

Thanks Guys.



I do see a little bit of field rotation, but it generally manifests as 0.01 degrees per 2 or 3 10 minute exposures, so isn't too bad.. The equipment I'm imaging with is a WO FLT110 refractor and modified Canon 350D DSLR, guided through a WO ZS66SD with Imaging Source DMK21 USB camera via GuideMaster software.. I have more of an issue with differential flexure, which I've managed to substantially reduce, and suspect the remaining 1-2 pixel drift per 10 min expsoure may be the FLT110 focuser sagging slightly, as I'm running out of other options.



To date I've been relying on Gemini to tell me the polar alignment error, as it does after you've aligned the 3rd and subsequent stars.. I then tweak alt & az, cold reset the mount, and start again - to hopefully observer a smaller error.. My observing position is kind of limited, and drift alignment is a bit tricky from there. - my view East is blocked by our house, and my wife's 2+m Jeruslem Artichokes currently obscure the view to the West, so my view is largely "Up", which is fine for imaging as I can usually get 3+hrs of imaging in for most objects if I catch them when they're just prior to straight up (ie. mount just rotated past the verticle).. Visually I'm as "on the pole" as I could be when I look through the scope, but that makes no allowance for less than perfect mounting which is bound to be the case.



While I've got a pier, it's the only bit that's permanent - the rest of my kit comes in every night.. It was my hope that once I got alignment good, and assuming alt and az is well locked down, I should be able to get repeatably close enough by just taking the mount out and plonking it down on the MA adapter.. This seems to be the case, but is one reason I have yet to get fussy about perfect alignment.



So, the plan looks like it should be to continue to chip away at better alignment but to not get too worried about being perfect.. Also not to worry about using Adaptive King.



Cheers & thanks,

Rod











---------------

From: Dave Kodama kodama@...>

To: Losmandy_users@yahoogroups.com

Sent: Friday, 20 February, 2009 8:09:14 PM

Subject: [Losmandy_users] Re: Polar Alignment / Guiding Tracking





Greg,



Sorry, I should have checked the manual first. I think you're

referring to "closed loop" tracking. This is OK for visual use but

being misaligned will still result in field rotation. Also, tracking

in the DEC axis will start to cause PE errors from that axis to

complicate the tracking errors.



Anyway, going back to the question of how good your polar alignment

has to be... how much rotation you can tolerate in a photo depends on

all the factors I mentioned earlier, so it's really not possible to

give one number which is good enough for all imaging setups. Shooting

4x5 film photos requires much, much more accurate alignment than

2-minute sub-exposures with an APS-sized DSLR sensor.



Dave

--- In Losmandy_users@ yahoogroups. com, "Dave Kodama" kodama@...> wrote:

>

> Greg,

>

> Aside from tweaking the tracking rate constants or periodic error

> correction which are RA-axis-only adjustments, I was not aware of any

> kind of tracking compensation that is done based on computed polar

> misalignment. For this to work, the mount would have to move in both

> RA and DEC. Can you explain the tracking error compensation you're

> referring to?

>

> Dave

>

>

> --- In Losmandy_users@ yahoogroups. com, "gnowellsct" tim71pos@> wrote:

> >

> > Actually Gemini has a tracking error compensation so the below is

> not strictly speaking

> > true. For shorter exposures, I'd guess five to ten minutes, a

> "kinda oK aligned scope" say

> > to within 15 arc minutes of the pole may not show that much field

> rotation to merit

> > zeroing in on the polar alignment.

> >

> > Wiser heads than me may have some views on that. But basically once

> the tracking is

> > working with a polar aligment compensation the only remaining issue

> is field rotation.

> > While field rortation is a big deal if you are using an alt-az mount

> without a wedge, once

> > you have gotten "pretty durn close" to polar aligned and have drift

> correction (like Gemini)

> > I don't think there'd be much need for a precise polar alignment

> except on real long

> > exposure work.

> >

> > maybe someone here can elaborate... .

> >

> > regards

> > Greg N

> >

> > --- In Losmandy_users@ yahoogroups. com, "Dave Kodama" kodama@> wrote:

> > >

> > > Rod,

> > >

> > > It's often a confusing issue, but the modeling (using lots of stars)

> > > is for go-to slewing accuracy and not tracking.

> > >

> > > If you want accurate tracking, you need to worry about polar

> > > alignment. How close it needs to be depends on your imaging

> > > requirements (how big your camera FOV is, how good your resolution,

> > > how long single exposures will be, etc.) I suggest aligning as well

> > > as you guess you need it to be, then do some test exposures and

see if

> > > you get field rotation in your shots. I think a lot of people sweat

> > > about really precise polar alignment without needing to.

> > >

> > > If you are guiding (i.e. using an autoguider or manually guiding the

> > > old way with an eyepiece), then the tracking rate you choose doesn't

> > > matter since the guiding will actively correct the mount's

tracking.

> > > So I just leave my mount set to sidereal tracking rate. The other

> > > tracking rates, including lunar and solar) are most useful in cases

> > > where you are *not* guiding like for visual use or say,

photographing

> > > a solar eclipse sequence.

> > >

> > > It's interesting that you found some odd interaction between the

King

> > > rate and the mount modeling, but I think that's not important. Just

> > > set it up using sidereal rate, then switch once you're done building

> > > the model. And as I said earlier, if you're guiding, just leave the

> > > mount in sidereal mode.

> > >

> > > Dave Kodama

> > >

> > >

> > > --- In Losmandy_users@ yahoogroups. com, Rod Mckay rodnscope@> wrote:

> > > >

> > > >

> > > > Hi,

> > > >

> > > > Couple of quesitons to the Guru's out there...

> > > >

> > > > 1. How close do people generally get their polar alignment in

> > > permanent installations? I'm in the process of setting up a

pier and

> > > can plonk the mount on and be within ~7' of the pole - is that

> > > reasonable, or should I spend more time trying to hone in closer?

> > > When adding more stars to the model it seems that the error jumps

> > > around by a few mninutes, so will I end up chasing my tail?

> > > >

> > > > I've previously tried using the Gemini polar alignment tools with

> > > varied success - it seems hit or miss whether you end up closer or

> not.

> > > >

> > > > 2. When auto guiding, do people generally have the mount set for

> > > Siderial or Adaptive King?

> > > >

> > > > 3. Is if odd that when using Siderial and doing a series of

> > > alignments I get a reported polar alignment error of ~ 7' on each

> > > axis, but when I do a number of alignments when set to Adaptive

King I

> > > get a reported polar alignment error of 30+' in each axis? I didn't

> > > touch the alt or az between alignments. Should I align on Siderial

> > > and then switch to Adaptive King?

> > > >

> > > > I'm sure I'll sort all this out in time, but I'd be interested to

> > > know if anyone has the answers.

> > > >

> > > > Cheers & thanks,

> > > > Rod

> > > >

> > > >

> > > > Make Yahoo!7 your homepage and win a trip to the Quiksilver

> > > Pro. Find out more

> > > >

> > >

> >

>











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----------------------------

#41832 Feb 20 1:32 AM

Rod,



Sounds like you're on the right path. Since you're using autoguiding,

there's no reason to mess with Adaptive King or anything but sidereal

rate.



The only thing I might suggest is to use the Gemini polar axis

correction routine rather than just depend on the error numbers

resulting from running the modeling procedure (I haven't used it

seriously myself except to try it as I use drift alignment normally).



Dave





--- In Losmandy_users@yahoogroups.com, Rod Mckay rodnscope@...> wrote:

>

> Thanks Guys.

>

> I do see a little bit of field rotation, but it generally manifests

as 0.01 degrees per 2 or 3 10 minute exposures, so isn't too bad.. The

equipment I'm imaging with is a WO FLT110 refractor and modified Canon

350D DSLR, guided through a WO ZS66SD with Imaging Source DMK21 USB

camera via GuideMaster software.. I have more of an issue with

differential flexure, which I've managed to substantially reduce, and

suspect the remaining 1-2 pixel drift per 10 min expsoure may be the

FLT110 focuser sagging slightly, as I'm running out of other options.

>

> To date I've been relying on Gemini to tell me the polar alignment

error, as it does after you've aligned the 3rd and subsequent stars..

I then tweak alt & az, cold reset the mount, and start again - to

hopefully observer a smaller error.. My observing position is kind of

limited, and drift alignment is a bit tricky from there. - my view

East is blocked by our house, and my wife's 2+m Jeruslem Artichokes

currently obscure the view to the West, so my view is largely "Up",

which is fine for imaging as I can usually get 3+hrs of imaging in for

most objects if I catch them when they're just prior to straight up

(ie. mount just rotated past the verticle).. Visually I'm as "on the

pole" as I could be when I look through the scope, but that makes no

allowance for less than perfect mounting which is bound to be the case.

>

> While I've got a pier, it's the only bit that's permanent - the rest

of my kit comes in every night.. It was my hope that once I got

alignment good, and assuming alt and az is well locked down, I should

be able to get repeatably close enough by just taking the mount out

and plonking it down on the MA adapter.. This seems to be the case,

but is one reason I have yet to get fussy about perfect alignment.

>

> So, the plan looks like it should be to continue to chip away at

better alignment but to not get too worried about being perfect.. Also

not to worry about using Adaptive King.

>

> Cheers & thanks,

> Rod

>

>

>

>

>

---------------

> From: Dave Kodama kodama@...>

> To: Losmandy_users@yahoogroups.com

> Sent: Friday, 20 February, 2009 8:09:14 PM

> Subject: [Losmandy_users] Re: Polar Alignment / Guiding Tracking

>

>

> Greg,

>

> Sorry, I should have checked the manual first. I think you're

> referring to "closed loop" tracking. This is OK for visual use but

> being misaligned will still result in field rotation. Also, tracking

> in the DEC axis will start to cause PE errors from that axis to

> complicate the tracking errors.

>

> Anyway, going back to the question of how good your polar alignment

> has to be... how much rotation you can tolerate in a photo depends on

> all the factors I mentioned earlier, so it's really not possible to

> give one number which is good enough for all imaging setups. Shooting

> 4x5 film photos requires much, much more accurate alignment than

> 2-minute sub-exposures with an APS-sized DSLR sensor.

>

> Dave

>

> --- In Losmandy_users@ yahoogroups. com, "Dave Kodama" kodama@> wrote:

> >

> > Greg,

> >

> > Aside from tweaking the tracking rate constants or periodic error

> > correction which are RA-axis-only adjustments, I was not aware of any

> > kind of tracking compensation that is done based on computed polar

> > misalignment. For this to work, the mount would have to move in both

> > RA and DEC. Can you explain the tracking error compensation you're

> > referring to?

> >

> > Dave

> >

> >

> > --- In Losmandy_users@ yahoogroups. com, "gnowellsct" tim71pos@>

wrote:

> > >

> > > Actually Gemini has a tracking error compensation so the below is

> > not strictly speaking

> > > true. For shorter exposures, I'd guess five to ten minutes, a

> > "kinda oK aligned scope" say

> > > to within 15 arc minutes of the pole may not show that much field

> > rotation to merit

> > > zeroing in on the polar alignment.

> > >

> > > Wiser heads than me may have some views on that. But basically once

> > the tracking is

> > > working with a polar aligment compensation the only remaining issue

> > is field rotation.

> > > While field rortation is a big deal if you are using an alt-az mount

> > without a wedge, once

> > > you have gotten "pretty durn close" to polar aligned and have drift

> > correction (like Gemini)

> > > I don't think there'd be much need for a precise polar alignment

> > except on real long

> > > exposure work.

> > >

> > > maybe someone here can elaborate... .

> > >

> > > regards

> > > Greg N

> > >

> > > --- In Losmandy_users@ yahoogroups. com, "Dave Kodama" kodama@>

wrote:

> > > >

> > > > Rod,

> > > >

> > > > It's often a confusing issue, but the modeling (using lots of

stars)

> > > > is for go-to slewing accuracy and not tracking.

> > > >

> > > > If you want accurate tracking, you need to worry about polar

> > > > alignment. How close it needs to be depends on your imaging

> > > > requirements (how big your camera FOV is, how good your

resolution,

> > > > how long single exposures will be, etc.) I suggest aligning as

well

> > > > as you guess you need it to be, then do some test exposures and

> see if

> > > > you get field rotation in your shots. I think a lot of people

sweat

> > > > about really precise polar alignment without needing to.

> > > >

> > > > If you are guiding (i.e. using an autoguider or manually

guiding the

> > > > old way with an eyepiece), then the tracking rate you choose

doesn't

> > > > matter since the guiding will actively correct the mount's

> tracking.

> > > > So I just leave my mount set to sidereal tracking rate. The other

> > > > tracking rates, including lunar and solar) are most useful in

cases

> > > > where you are *not* guiding like for visual use or say,

> photographing

> > > > a solar eclipse sequence.

> > > >

> > > > It's interesting that you found some odd interaction between the

> King

> > > > rate and the mount modeling, but I think that's not important.

Just

> > > > set it up using sidereal rate, then switch once you're done

building

> > > > the model. And as I said earlier, if you're guiding, just

leave the

> > > > mount in sidereal mode.

> > > >

> > > > Dave Kodama

> > > >

> > > >

> > > > --- In Losmandy_users@ yahoogroups. com, Rod Mckay

rodnscope@> wrote:

> > > > >

> > > > >

> > > > > Hi,

> > > > >

> > > > > Couple of quesitons to the Guru's out there...

> > > > >

> > > > > 1. How close do people generally get their polar alignment in

> > > > permanent installations? I'm in the process of setting up a

> pier and

> > > > can plonk the mount on and be within ~7' of the pole - is that

> > > > reasonable, or should I spend more time trying to hone in closer?

> > > > When adding more stars to the model it seems that the error jumps

> > > > around by a few mninutes, so will I end up chasing my tail?

> > > > >

> > > > > I've previously tried using the Gemini polar alignment tools

with

> > > > varied success - it seems hit or miss whether you end up closer or

> > not.

> > > > >

> > > > > 2. When auto guiding, do people generally have the mount set for

> > > > Siderial or Adaptive King?

> > > > >

> > > > > 3. Is if odd that when using Siderial and doing a series of

> > > > alignments I get a reported polar alignment error of ~ 7' on each

> > > > axis, but when I do a number of alignments when set to Adaptive

> King I

> > > > get a reported polar alignment error of 30+' in each axis? I

didn't

> > > > touch the alt or az between alignments. Should I align on Siderial

> > > > and then switch to Adaptive King?

> > > > >

> > > > > I'm sure I'll sort all this out in time, but I'd be

interested to

> > > > know if anyone has the answers.

> > > > >

> > > > > Cheers & thanks,

> > > > > Rod

> > > > >

> > > > >

> > > > > Make Yahoo!7 your homepage and win a trip to the Quiksilver

> > > > Pro. Find out more

> > > > >

> > > >

> > >

> >

>

>

>

>

>

> Stay connected to the people that matter most with a smarter

inbox. Take a look au.docs.yahoo.com/mail/smarterinbox

>

> [Non-text portions of this message have been removed]

>







----------------------------

#41836 Feb 20 11:19 AM

Right: you've got a closed loop option. The problem of field rotation

and Dec PE will be directly related to how far off true N you are. My

accuracy with teh Losmandy polar scope ranges from perfect (within the

measurement accuracy of Argo Navis and 10k dscs) to about 12 minutes

off depending on the night. I don't think 12 arc minutes is going to

cause a whole lot of problems but then again that would depend on what

the person is trying to do, including the fl of the instrument and the

exposure lengths he is trying to achieve. I would think that 30 and 60

arc minute polar alignment errors would start to be unacceptable for

photography. My guess is that 10 arc minutes and under with closed

loop correction is probably good nuff for most folks.



I'm not sure one would need the closed loop utility with an autoguider.



regards

Greg N

--- In Losmandy_users@yahoogroups.com, "Dave Kodama" kodama@...> wrote:

>

> Greg,

>

> Sorry, I should have checked the manual first. I think you're

> referring to "closed loop" tracking. This is OK for visual use but

> being misaligned will still result in field rotation. Also, tracking

> in the DEC axis will start to cause PE errors from that axis to

> complicate the tracking errors.



----------------------------

#41837 Feb 20 1:55 PM

If the closed loop mode moved the scope in anticipation of where it

should be, it should *theoretically* help autoguiding, but like PEC,

it could interact badly if the mount corrections were delayed or

incorrect with respect to the real sky position.



My inclination would be to leave it off when autoguiding. After all,

using an autoguider is truly closing the loop with reference to what

it's actually seeing as opposed to where the mount thinks it should be

pointing. Anyway, if the mount alignment is so far off that it's

making a big difference, then field rotation will be an issue.



Dave



> I'm not sure one would need the closed loop utility with an autoguider.



----------------------------

#43835 Sep 2, 2009

Dave,



I pretty new to using my new GM-8 with Gemini. I see from your post below that you use drift alignment for Astrophotography. I've been attempting to find out the procedures, step-by-step, that are necessaary to drift align my system.



Questions I have are whether or not to do modeling, etc prior to drift alignment?? Do you slew the scope to alignment stars or can one simply use the clutches to get the scope close and then slew to get the star centered??



Anyway, I really need some help with this deal as I'm interested in fairly long exposure periods without error.



Thanks,

Jerry.



--- In Losmandy_users@yahoogroups.com, "Dave Kodama" kodama@...> wrote:

>

> Rod,

>

> Sounds like you're on the right path. Since you're using autoguiding,

> there's no reason to mess with Adaptive King or anything but sidereal

> rate.

>

> The only thing I might suggest is to use the Gemini polar axis

> correction routine rather than just depend on the error numbers

> resulting from running the modeling procedure (I haven't used it

> seriously myself except to try it as I use drift alignment normally).

>

> Dave

>

>

>

> --- In Losmandy_users@yahoogroups.com, Rod Mckay rodnscope@> wrote:

> >

> > Thanks Guys.

> >

> > I do see a little bit of field rotation, but it generally manifests

> as 0.01 degrees per 2 or 3 10 minute exposures, so isn't too bad.. The

> equipment I'm imaging with is a WO FLT110 refractor and modified Canon

> 350D DSLR, guided through a WO ZS66SD with Imaging Source DMK21 USB

> camera via GuideMaster software.. I have more of an issue with

> differential flexure, which I've managed to substantially reduce, and

> suspect the remaining 1-2 pixel drift per 10 min expsoure may be the

> FLT110 focuser sagging slightly, as I'm running out of other options.

> >

> > To date I've been relying on Gemini to tell me the polar alignment

> error, as it does after you've aligned the 3rd and subsequent stars..

> I then tweak alt & az, cold reset the mount, and start again - to

> hopefully observer a smaller error.. My observing position is kind of

> limited, and drift alignment is a bit tricky from there. - my view

> East is blocked by our house, and my wife's 2+m Jeruslem Artichokes

> currently obscure the view to the West, so my view is largely "Up",

> which is fine for imaging as I can usually get 3+hrs of imaging in for

> most objects if I catch them when they're just prior to straight up

> (ie. mount just rotated past the verticle).. Visually I'm as "on the

> pole" as I could be when I look through the scope, but that makes no

> allowance for less than perfect mounting which is bound to be the case.

> >

> > While I've got a pier, it's the only bit that's permanent - the rest

> of my kit comes in every night.. It was my hope that once I got

> alignment good, and assuming alt and az is well locked down, I should

> be able to get repeatably close enough by just taking the mount out

> and plonking it down on the MA adapter.. This seems to be the case,

> but is one reason I have yet to get fussy about perfect alignment.

> >

> > So, the plan looks like it should be to continue to chip away at

> better alignment but to not get too worried about being perfect.. Also

> not to worry about using Adaptive King.

> >

> > Cheers & thanks,

> > Rod

> >

> >

> >

> >

> >

---------------

> > From: Dave Kodama kodama@>

> > To: Losmandy_users@yahoogroups.com

> > Sent: Friday, 20 February, 2009 8:09:14 PM

> > Subject: [Losmandy_users] Re: Polar Alignment / Guiding Tracking

> >

> >

> > Greg,

> >

> > Sorry, I should have checked the manual first. I think you're

> > referring to "closed loop" tracking. This is OK for visual use but

> > being misaligned will still result in field rotation. Also, tracking

> > in the DEC axis will start to cause PE errors from that axis to

> > complicate the tracking errors.

> >

> > Anyway, going back to the question of how good your polar alignment

> > has to be... how much rotation you can tolerate in a photo depends on

> > all the factors I mentioned earlier, so it's really not possible to

> > give one number which is good enough for all imaging setups. Shooting

> > 4x5 film photos requires much, much more accurate alignment than

> > 2-minute sub-exposures with an APS-sized DSLR sensor.

> >

> > Dave

> >

> > --- In Losmandy_users@ yahoogroups. com, "Dave Kodama" kodama@> wrote:

> > >

> > > Greg,

> > >

> > > Aside from tweaking the tracking rate constants or periodic error

> > > correction which are RA-axis-only adjustments, I was not aware of any

> > > kind of tracking compensation that is done based on computed polar

> > > misalignment. For this to work, the mount would have to move in both

> > > RA and DEC. Can you explain the tracking error compensation you're

> > > referring to?

> > >

> > > Dave

> > >

> > >

> > > --- In Losmandy_users@ yahoogroups. com, "gnowellsct" tim71pos@>

> wrote:

> > > >

> > > > Actually Gemini has a tracking error compensation so the below is

> > > not strictly speaking

> > > > true. For shorter exposures, I'd guess five to ten minutes, a

> > > "kinda oK aligned scope" say

> > > > to within 15 arc minutes of the pole may not show that much field

> > > rotation to merit

> > > > zeroing in on the polar alignment.

> > > >

> > > > Wiser heads than me may have some views on that. But basically once

> > > the tracking is

> > > > working with a polar aligment compensation the only remaining issue

> > > is field rotation.

> > > > While field rortation is a big deal if you are using an alt-az mount

> > > without a wedge, once

> > > > you have gotten "pretty durn close" to polar aligned and have drift

> > > correction (like Gemini)

> > > > I don't think there'd be much need for a precise polar alignment

> > > except on real long

> > > > exposure work.

> > > >

> > > > maybe someone here can elaborate... .

> > > >

> > > > regards

> > > > Greg N

> > > >

> > > > --- In Losmandy_users@ yahoogroups. com, "Dave Kodama" kodama@>

> wrote:

> > > > >

> > > > > Rod,

> > > > >

> > > > > It's often a confusing issue, but the modeling (using lots of

> stars)

> > > > > is for go-to slewing accuracy and not tracking.

> > > > >

> > > > > If you want accurate tracking, you need to worry about polar

> > > > > alignment. How close it needs to be depends on your imaging

> > > > > requirements (how big your camera FOV is, how good your

> resolution,

> > > > > how long single exposures will be, etc.) I suggest aligning as

> well

> > > > > as you guess you need it to be, then do some test exposures and

> > see if

> > > > > you get field rotation in your shots. I think a lot of people

> sweat

> > > > > about really precise polar alignment without needing to.

> > > > >

> > > > > If you are guiding (i.e. using an autoguider or manually

> guiding the

> > > > > old way with an eyepiece), then the tracking rate you choose

> doesn't

> > > > > matter since the guiding will actively correct the mount's

> > tracking.

> > > > > So I just leave my mount set to sidereal tracking rate. The other

> > > > > tracking rates, including lunar and solar) are most useful in

> cases

> > > > > where you are *not* guiding like for visual use or say,

> > photographing

> > > > > a solar eclipse sequence.

> > > > >

> > > > > It's interesting that you found some odd interaction between the

> > King

> > > > > rate and the mount modeling, but I think that's not important.

> Just

> > > > > set it up using sidereal rate, then switch once you're done

> building

> > > > > the model. And as I said earlier, if you're guiding, just

> leave the

> > > > > mount in sidereal mode.

> > > > >

> > > > > Dave Kodama

> > > > >

> > > > >

> > > > > --- In Losmandy_users@ yahoogroups. com, Rod Mckay

> rodnscope@> wrote:

> > > > > >

> > > > > >

> > > > > > Hi,

> > > > > >

> > > > > > Couple of quesitons to the Guru's out there...

> > > > > >

> > > > > > 1. How close do people generally get their polar alignment in

> > > > > permanent installations? I'm in the process of setting up a

> > pier and

> > > > > can plonk the mount on and be within ~7' of the pole - is that

> > > > > reasonable, or should I spend more time trying to hone in closer?

> > > > > When adding more stars to the model it seems that the error jumps

> > > > > around by a few mninutes, so will I end up chasing my tail?

> > > > > >

> > > > > > I've previously tried using the Gemini polar alignment tools

> with

> > > > > varied success - it seems hit or miss whether you end up closer or

> > > not.

> > > > > >

> > > > > > 2. When auto guiding, do people generally have the mount set for

> > > > > Siderial or Adaptive King?

> > > > > >

> > > > > > 3. Is if odd that when using Siderial and doing a series of

> > > > > alignments I get a reported polar alignment error of ~ 7' on each

> > > > > axis, but when I do a number of alignments when set to Adaptive

> > King I

> > > > > get a reported polar alignment error of 30+' in each axis? I

> didn't

> > > > > touch the alt or az between alignments. Should I align on Siderial

> > > > > and then switch to Adaptive King?

> > > > > >

> > > > > > I'm sure I'll sort all this out in time, but I'd be

> interested to

> > > > > know if anyone has the answers.

> > > > > >

> > > > > > Cheers & thanks,

> > > > > > Rod

> > > > > >

> > > > > >

> > > > > > Make Yahoo!7 your homepage and win a trip to the Quiksilver

> > > > > Pro. Find out more

> > > > > >

> > > > >

> > > >

> > >

> >

> >

> >

> >

> >

> > Stay connected to the people that matter most with a smarter

> inbox. Take a look au.docs.yahoo.com/mail/smarterinbox

> >

> > [Non-text portions of this message have been removed]

> >

>







----------------------------

#43837 Sep 2, 2009

Jerry,



I do drift alignment first. Or you can use the iterative Gemini procedures to align.



Either way, for accurate tracking for long exposures, you want to set your mount's altitude and azimuth adjustment accurately *first*. Then do your modeling, which is used for go-to slews.



When doing your modeling for the first time, you first want to power up in the counterweight-down position with a cold-start. This is so the Gemini knows where the mount is positioned physically to start. It's important to start up properly so the slews don't cause the mount to go past the safety limits. After this is done, you never should release the clutches.



The modeling is done by letting the Gemini slew to the selected alignment stars. Assuming you have set the correct time and other mount parameters, it should slew fairly close to the first alignment star you select, then you use the paddle to tweak the position in your scope (i.e. not by releasing the clutches). Subsequent alignment stars are handled the same way and you should find the Gemini slews getting closer and closer to being right on target.



If I'm just going to be doing long exposures and not requiring a lot of accurate slewing (e.g. for a night of widefield shots), after polar axis alignment, I just use one star or just a small handful for the model (after clearing out any old model remaining in memory).



Dave



--- In Losmandy_users@yahoogroups.com, "ott_je" jc.ott@...> wrote:

>

>

> Dave,

>

> I pretty new to using my new GM-8 with Gemini. I see from your post below that you use drift alignment for Astrophotography. I've been attempting to find out the procedures, step-by-step, that are necessaary to drift align my system.

>

> Questions I have are whether or not to do modeling, etc prior to drift alignment?? Do you slew the scope to alignment stars or can one simply use the clutches to get the scope close and then slew to get the star centered??

>

> Anyway, I really need some help with this deal as I'm interested in fairly long exposure periods without error.

>

> Thanks,

> Jerry.

>

>

> --- In Losmandy_users@yahoogroups.com, "Dave Kodama" kodama@> wrote:

> >

> > Rod,

> >

> > Sounds like you're on the right path. Since you're using autoguiding,

> > there's no reason to mess with Adaptive King or anything but sidereal

> > rate.

> >

> > The only thing I might suggest is to use the Gemini polar axis

> > correction routine rather than just depend on the error numbers

> > resulting from running the modeling procedure (I haven't used it

> > seriously myself except to try it as I use drift alignment normally).

> >

> > Dave

> >

> >

> >

> > --- In Losmandy_users@yahoogroups.com, Rod Mckay rodnscope@> wrote:

> > >

> > > Thanks Guys.

> > >

> > > I do see a little bit of field rotation, but it generally manifests

> > as 0.01 degrees per 2 or 3 10 minute exposures, so isn't too bad.. The

> > equipment I'm imaging with is a WO FLT110 refractor and modified Canon

> > 350D DSLR, guided through a WO ZS66SD with Imaging Source DMK21 USB

> > camera via GuideMaster software.. I have more of an issue with

> > differential flexure, which I've managed to substantially reduce, and

> > suspect the remaining 1-2 pixel drift per 10 min expsoure may be the

> > FLT110 focuser sagging slightly, as I'm running out of other options.

> > >

> > > To date I've been relying on Gemini to tell me the polar alignment

> > error, as it does after you've aligned the 3rd and subsequent stars..

> > I then tweak alt & az, cold reset the mount, and start again - to

> > hopefully observer a smaller error.. My observing position is kind of

> > limited, and drift alignment is a bit tricky from there. - my view

> > East is blocked by our house, and my wife's 2+m Jeruslem Artichokes

> > currently obscure the view to the West, so my view is largely "Up",

> > which is fine for imaging as I can usually get 3+hrs of imaging in for

> > most objects if I catch them when they're just prior to straight up

> > (ie. mount just rotated past the verticle).. Visually I'm as "on the

> > pole" as I could be when I look through the scope, but that makes no

> > allowance for less than perfect mounting which is bound to be the case.

> > >

> > > While I've got a pier, it's the only bit that's permanent - the rest

> > of my kit comes in every night.. It was my hope that once I got

> > alignment good, and assuming alt and az is well locked down, I should

> > be able to get repeatably close enough by just taking the mount out

> > and plonking it down on the MA adapter.. This seems to be the case,

> > but is one reason I have yet to get fussy about perfect alignment.

> > >

> > > So, the plan looks like it should be to continue to chip away at

> > better alignment but to not get too worried about being perfect.. Also

> > not to worry about using Adaptive King.

> > >

> > > Cheers & thanks,

> > > Rod

> > >

> > >

> > >

> > >

> > >

---------------

> > > From: Dave Kodama kodama@>

> > > To: Losmandy_users@yahoogroups.com

> > > Sent: Friday, 20 February, 2009 8:09:14 PM

> > > Subject: [Losmandy_users] Re: Polar Alignment / Guiding Tracking

> > >

> > >

> > > Greg,

> > >

> > > Sorry, I should have checked the manual first. I think you're

> > > referring to "closed loop" tracking. This is OK for visual use but

> > > being misaligned will still result in field rotation. Also, tracking

> > > in the DEC axis will start to cause PE errors from that axis to

> > > complicate the tracking errors.

> > >

> > > Anyway, going back to the question of how good your polar alignment

> > > has to be... how much rotation you can tolerate in a photo depends on

> > > all the factors I mentioned earlier, so it's really not possible to

> > > give one number which is good enough for all imaging setups. Shooting

> > > 4x5 film photos requires much, much more accurate alignment than

> > > 2-minute sub-exposures with an APS-sized DSLR sensor.

> > >

> > > Dave

> > >

> > > --- In Losmandy_users@ yahoogroups. com, "Dave Kodama" kodama@> wrote:

> > > >

> > > > Greg,

> > > >

> > > > Aside from tweaking the tracking rate constants or periodic error

> > > > correction which are RA-axis-only adjustments, I was not aware of any

> > > > kind of tracking compensation that is done based on computed polar

> > > > misalignment. For this to work, the mount would have to move in both

> > > > RA and DEC. Can you explain the tracking error compensation you're

> > > > referring to?

> > > >

> > > > Dave

> > > >

> > > >

> > > > --- In Losmandy_users@ yahoogroups. com, "gnowellsct" tim71pos@>

> > wrote:

> > > > >

> > > > > Actually Gemini has a tracking error compensation so the below is

> > > > not strictly speaking

> > > > > true. For shorter exposures, I'd guess five to ten minutes, a

> > > > "kinda oK aligned scope" say

> > > > > to within 15 arc minutes of the pole may not show that much field

> > > > rotation to merit

> > > > > zeroing in on the polar alignment.

> > > > >

> > > > > Wiser heads than me may have some views on that. But basically once

> > > > the tracking is

> > > > > working with a polar aligment compensation the only remaining issue

> > > > is field rotation.

> > > > > While field rortation is a big deal if you are using an alt-az mount

> > > > without a wedge, once

> > > > > you have gotten "pretty durn close" to polar aligned and have drift

> > > > correction (like Gemini)

> > > > > I don't think there'd be much need for a precise polar alignment

> > > > except on real long

> > > > > exposure work.

> > > > >

> > > > > maybe someone here can elaborate... .

> > > > >

> > > > > regards

> > > > > Greg N

> > > > >

> > > > > --- In Losmandy_users@ yahoogroups. com, "Dave Kodama" kodama@>

> > wrote:

> > > > > >

> > > > > > Rod,

> > > > > >

> > > > > > It's often a confusing issue, but the modeling (using lots of

> > stars)

> > > > > > is for go-to slewing accuracy and not tracking.

> > > > > >

> > > > > > If you want accurate tracking, you need to worry about polar

> > > > > > alignment. How close it needs to be depends on your imaging

> > > > > > requirements (how big your camera FOV is, how good your

> > resolution,

> > > > > > how long single exposures will be, etc.) I suggest aligning as

> > well

> > > > > > as you guess you need it to be, then do some test exposures and

> > > see if

> > > > > > you get field rotation in your shots. I think a lot of people

> > sweat

> > > > > > about really precise polar alignment without needing to.

> > > > > >

> > > > > > If you are guiding (i.e. using an autoguider or manually

> > guiding the

> > > > > > old way with an eyepiece), then the tracking rate you choose

> > doesn't

> > > > > > matter since the guiding will actively correct the mount's

> > > tracking.

> > > > > > So I just leave my mount set to sidereal tracking rate. The other

> > > > > > tracking rates, including lunar and solar) are most useful in

> > cases

> > > > > > where you are *not* guiding like for visual use or say,

> > > photographing

> > > > > > a solar eclipse sequence.

> > > > > >

> > > > > > It's interesting that you found some odd interaction between the

> > > King

> > > > > > rate and the mount modeling, but I think that's not important.

> > Just

> > > > > > set it up using sidereal rate, then switch once you're done

> > building

> > > > > > the model. And as I said earlier, if you're guiding, just

> > leave the

> > > > > > mount in sidereal mode.

> > > > > >

> > > > > > Dave Kodama

> > > > > >

> > > > > >

> > > > > > --- In Losmandy_users@ yahoogroups. com, Rod Mckay

> > rodnscope@> wrote:

> > > > > > >

> > > > > > >

> > > > > > > Hi,

> > > > > > >

> > > > > > > Couple of quesitons to the Guru's out there...

> > > > > > >

> > > > > > > 1. How close do people generally get their polar alignment in

> > > > > > permanent installations? I'm in the process of setting up a

> > > pier and

> > > > > > can plonk the mount on and be within ~7' of the pole - is that

> > > > > > reasonable, or should I spend more time trying to hone in closer?

> > > > > > When adding more stars to the model it seems that the error jumps

> > > > > > around by a few mninutes, so will I end up chasing my tail?

> > > > > > >

> > > > > > > I've previously tried using the Gemini polar alignment tools

> > with

> > > > > > varied success - it seems hit or miss whether you end up closer or

> > > > not.

> > > > > > >

> > > > > > > 2. When auto guiding, do people generally have the mount set for

> > > > > > Siderial or Adaptive King?

> > > > > > >

> > > > > > > 3. Is if odd that when using Siderial and doing a series of

> > > > > > alignments I get a reported polar alignment error of ~ 7' on each

> > > > > > axis, but when I do a number of alignments when set to Adaptive

> > > King I

> > > > > > get a reported polar alignment error of 30+' in each axis? I

> > didn't

> > > > > > touch the alt or az between alignments. Should I align on Siderial

> > > > > > and then switch to Adaptive King?

> > > > > > >

> > > > > > > I'm sure I'll sort all this out in time, but I'd be

> > interested to

> > > > > > know if anyone has the answers.

> > > > > > >

> > > > > > > Cheers & thanks,

> > > > > > > Rod

> > > > > > >

> > > > > > >

> > > > > > > Make Yahoo!7 your homepage and win a trip to the Quiksilver

> > > > > > Pro. Find out more

> > > > > > >

> > > > > >

> > > > >

> > > >

> > >

> > >

> > >

> > >

> > >

> > > Stay connected to the people that matter most with a smarter

> > inbox. Take a look au.docs.yahoo.com/mail/smarterinbox

> > >

> > > [Non-text portions of this message have been removed]

> > >

> >

>







----------------------------

#43838 Sep 2, 2009

I used to just use the polar scope and then check tracking to Make sure my Y drift wasn't too bad. Now I use PemPro's Polar alignment tool which can sniff out polar misalignment within 1 arc minute in each axis. It still takes half an hour to do a good drift but the effort pays off.



Love ccdware stuff!

--- In Losmandy_users@yahoogroups.com, "d_kodama" kodama@...> wrote:

>

> Jerry,

>

> I do drift alignment first. Or you can use the iterative Gemini procedures to align.

>

> Either way, for accurate tracking for long exposures, you want to set your mount's altitude and azimuth adjustment accurately *first*. Then do your modeling, which is used for go-to slews.

>

> When doing your modeling for the first time, you first want to power up in the counterweight-down position with a cold-start. This is so the Gemini knows where the mount is positioned physically to start. It's important to start up properly so the slews don't cause the mount to go past the safety limits. After this is done, you never should release the clutches.

>

> The modeling is done by letting the Gemini slew to the selected alignment stars. Assuming you have set the correct time and other mount parameters, it should slew fairly close to the first alignment star you select, then you use the paddle to tweak the position in your scope (i.e. not by releasing the clutches). Subsequent alignment stars are handled the same way and you should find the Gemini slews getting closer and closer to being right on target.

>

> If I'm just going to be doing long exposures and not requiring a lot of accurate slewing (e.g. for a night of widefield shots), after polar axis alignment, I just use one star or just a small handful for the model (after clearing out any old model remaining in memory).

>

> Dave

>

>

> --- In Losmandy_users@yahoogroups.com, "ott_je" jc.ott@> wrote:

> >

> >

> > Dave,

> >

> > I pretty new to using my new GM-8 with Gemini. I see from your post below that you use drift alignment for Astrophotography. I've been attempting to find out the procedures, step-by-step, that are necessaary to drift align my system.

> >

> > Questions I have are whether or not to do modeling, etc prior to drift alignment?? Do you slew the scope to alignment stars or can one simply use the clutches to get the scope close and then slew to get the star centered??

> >

> > Anyway, I really need some help with this deal as I'm interested in fairly long exposure periods without error.

> >

> > Thanks,

> > Jerry.

> >

> >

> > --- In Losmandy_users@yahoogroups.com, "Dave Kodama" kodama@> wrote:

> > >

> > > Rod,

> > >

> > > Sounds like you're on the right path. Since you're using autoguiding,

> > > there's no reason to mess with Adaptive King or anything but sidereal

> > > rate.

> > >

> > > The only thing I might suggest is to use the Gemini polar axis

> > > correction routine rather than just depend on the error numbers

> > > resulting from running the modeling procedure (I haven't used it

> > > seriously myself except to try it as I use drift alignment normally).

> > >

> > > Dave

> > >

> > >

> > >

> > > --- In Losmandy_users@yahoogroups.com, Rod Mckay rodnscope@> wrote:

> > > >

> > > > Thanks Guys.

> > > >

> > > > I do see a little bit of field rotation, but it generally manifests

> > > as 0.01 degrees per 2 or 3 10 minute exposures, so isn't too bad.. The

> > > equipment I'm imaging with is a WO FLT110 refractor and modified Canon

> > > 350D DSLR, guided through a WO ZS66SD with Imaging Source DMK21 USB

> > > camera via GuideMaster software.. I have more of an issue with

> > > differential flexure, which I've managed to substantially reduce, and

> > > suspect the remaining 1-2 pixel drift per 10 min expsoure may be the

> > > FLT110 focuser sagging slightly, as I'm running out of other options.

> > > >

> > > > To date I've been relying on Gemini to tell me the polar alignment

> > > error, as it does after you've aligned the 3rd and subsequent stars..

> > > I then tweak alt & az, cold reset the mount, and start again - to

> > > hopefully observer a smaller error.. My observing position is kind of

> > > limited, and drift alignment is a bit tricky from there. - my view

> > > East is blocked by our house, and my wife's 2+m Jeruslem Artichokes

> > > currently obscure the view to the West, so my view is largely "Up",

> > > which is fine for imaging as I can usually get 3+hrs of imaging in for

> > > most objects if I catch them when they're just prior to straight up

> > > (ie. mount just rotated past the verticle).. Visually I'm as "on the

> > > pole" as I could be when I look through the scope, but that makes no

> > > allowance for less than perfect mounting which is bound to be the case.

> > > >

> > > > While I've got a pier, it's the only bit that's permanent - the rest

> > > of my kit comes in every night.. It was my hope that once I got

> > > alignment good, and assuming alt and az is well locked down, I should

> > > be able to get repeatably close enough by just taking the mount out

> > > and plonking it down on the MA adapter.. This seems to be the case,

> > > but is one reason I have yet to get fussy about perfect alignment.

> > > >

> > > > So, the plan looks like it should be to continue to chip away at

> > > better alignment but to not get too worried about being perfect.. Also

> > > not to worry about using Adaptive King.

> > > >

> > > > Cheers & thanks,

> > > > Rod

> > > >

> > > >

> > > >

> > > >

> > > >

---------------

> > > > From: Dave Kodama kodama@>

> > > > To: Losmandy_users@yahoogroups.com

> > > > Sent: Friday, 20 February, 2009 8:09:14 PM

> > > > Subject: [Losmandy_users] Re: Polar Alignment / Guiding Tracking

> > > >

> > > >

> > > > Greg,

> > > >

> > > > Sorry, I should have checked the manual first. I think you're

> > > > referring to "closed loop" tracking. This is OK for visual use but

> > > > being misaligned will still result in field rotation. Also, tracking

> > > > in the DEC axis will start to cause PE errors from that axis to

> > > > complicate the tracking errors.

> > > >

> > > > Anyway, going back to the question of how good your polar alignment

> > > > has to be... how much rotation you can tolerate in a photo depends on

> > > > all the factors I mentioned earlier, so it's really not possible to

> > > > give one number which is good enough for all imaging setups. Shooting

> > > > 4x5 film photos requires much, much more accurate alignment than

> > > > 2-minute sub-exposures with an APS-sized DSLR sensor.

> > > >

> > > > Dave

> > > >

> > > > --- In Losmandy_users@ yahoogroups. com, "Dave Kodama" kodama@> wrote:

> > > > >

> > > > > Greg,

> > > > >

> > > > > Aside from tweaking the tracking rate constants or periodic error

> > > > > correction which are RA-axis-only adjustments, I was not aware of any

> > > > > kind of tracking compensation that is done based on computed polar

> > > > > misalignment. For this to work, the mount would have to move in both

> > > > > RA and DEC. Can you explain the tracking error compensation you're

> > > > > referring to?

> > > > >

> > > > > Dave

> > > > >

> > > > >

> > > > > --- In Losmandy_users@ yahoogroups. com, "gnowellsct" tim71pos@>

> > > wrote:

> > > > > >

> > > > > > Actually Gemini has a tracking error compensation so the below is

> > > > > not strictly speaking

> > > > > > true. For shorter exposures, I'd guess five to ten minutes, a

> > > > > "kinda oK aligned scope" say

> > > > > > to within 15 arc minutes of the pole may not show that much field

> > > > > rotation to merit

> > > > > > zeroing in on the polar alignment.

> > > > > >

> > > > > > Wiser heads than me may have some views on that. But basically once

> > > > > the tracking is

> > > > > > working with a polar aligment compensation the only remaining issue

> > > > > is field rotation.

> > > > > > While field rortation is a big deal if you are using an alt-az mount

> > > > > without a wedge, once

> > > > > > you have gotten "pretty durn close" to polar aligned and have drift

> > > > > correction (like Gemini)

> > > > > > I don't think there'd be much need for a precise polar alignment

> > > > > except on real long

> > > > > > exposure work.

> > > > > >

> > > > > > maybe someone here can elaborate... .

> > > > > >

> > > > > > regards

> > > > > > Greg N

> > > > > >

> > > > > > --- In Losmandy_users@ yahoogroups. com, "Dave Kodama" kodama@>

> > > wrote:

> > > > > > >

> > > > > > > Rod,

> > > > > > >

> > > > > > > It's often a confusing issue, but the modeling (using lots of

> > > stars)

> > > > > > > is for go-to slewing accuracy and not tracking.

> > > > > > >

> > > > > > > If you want accurate tracking, you need to worry about polar

> > > > > > > alignment. How close it needs to be depends on your imaging

> > > > > > > requirements (how big your camera FOV is, how good your

> > > resolution,

> > > > > > > how long single exposures will be, etc.) I suggest aligning as

> > > well

> > > > > > > as you guess you need it to be, then do some test exposures and

> > > > see if

> > > > > > > you get field rotation in your shots. I think a lot of people

> > > sweat

> > > > > > > about really precise polar alignment without needing to.

> > > > > > >

> > > > > > > If you are guiding (i.e. using an autoguider or manually

> > > guiding the

> > > > > > > old way with an eyepiece), then the tracking rate you choose

> > > doesn't

> > > > > > > matter since the guiding will actively correct the mount's

> > > > tracking.

> > > > > > > So I just leave my mount set to sidereal tracking rate. The other

> > > > > > > tracking rates, including lunar and solar) are most useful in

> > > cases

> > > > > > > where you are *not* guiding like for visual use or say,

> > > > photographing

> > > > > > > a solar eclipse sequence.

> > > > > > >

> > > > > > > It's interesting that you found some odd interaction between the

> > > > King

> > > > > > > rate and the mount modeling, but I think that's not important.

> > > Just

> > > > > > > set it up using sidereal rate, then switch once you're done

> > > building

> > > > > > > the model. And as I said earlier, if you're guiding, just

> > > leave the

> > > > > > > mount in sidereal mode.

> > > > > > >

> > > > > > > Dave Kodama

> > > > > > >

> > > > > > >

> > > > > > > --- In Losmandy_users@ yahoogroups. com, Rod Mckay

> > > rodnscope@> wrote:

> > > > > > > >

> > > > > > > >

> > > > > > > > Hi,

> > > > > > > >

> > > > > > > > Couple of quesitons to the Guru's out there...

> > > > > > > >

> > > > > > > > 1. How close do people generally get their polar alignment in

> > > > > > > permanent installations? I'm in the process of setting up a

> > > > pier and

> > > > > > > can plonk the mount on and be within ~7' of the pole - is that

> > > > > > > reasonable, or should I spend more time trying to hone in closer?

> > > > > > > When adding more stars to the model it seems that the error jumps

> > > > > > > around by a few mninutes, so will I end up chasing my tail?

> > > > > > > >

> > > > > > > > I've previously tried using the Gemini polar alignment tools

> > > with

> > > > > > > varied success - it seems hit or miss whether you end up closer or

> > > > > not.

> > > > > > > >

> > > > > > > > 2. When auto guiding, do people generally have the mount set for

> > > > > > > Siderial or Adaptive King?

> > > > > > > >

> > > > > > > > 3. Is if odd that when using Siderial and doing a series of

> > > > > > > alignments I get a reported polar alignment error of ~ 7' on each

> > > > > > > axis, but when I do a number of alignments when set to Adaptive

> > > > King I

> > > > > > > get a reported polar alignment error of 30+' in each axis? I

> > > didn't

> > > > > > > touch the alt or az between alignments. Should I align on Siderial

> > > > > > > and then switch to Adaptive King?

> > > > > > > >

> > > > > > > > I'm sure I'll sort all this out in time, but I'd be

> > > interested to

> > > > > > > know if anyone has the answers.

> > > > > > > >

> > > > > > > > Cheers & thanks,

> > > > > > > > Rod

> > > > > > > >

> > > > > > > >

> > > > > > > > Make Yahoo!7 your homepage and win a trip to the Quiksilver

> > > > > > > Pro. Find out more

> > > > > > > >

> > > > > > >

> > > > > >

> > > > >

> > > >

> > > >

> > > >

> > > >

> > > >

> > > > Stay connected to the people that matter most with a smarter

> > > inbox. Take a look au.docs.yahoo.com/mail/smarterinbox

> > > >

> > > > [Non-text portions of this message have been removed]

> > > >

> > >

> >

>







----------------------------

#43840 Sep 2, 2009

I just recently purchased a Gemini Losmandy mount. I do all the procedures that you describe. I slew to the first star, it is just on the edge of the FOV. My problem is centering the star. I went back and checked the manual, and it said to use the buttons RA+- or Dec+- to center the star. When I do this the mount will not move. What I'm I missing?







Gil



----- Original Message -----

From: "tpiccian" tpicciani@...>

To: "Losmandy users" Losmandy_users@yahoogroups.com>

Sent: Wednesday, September 2, 2009 11:52:13 AM GMT -05:00 US/Canada Eastern

Subject: [Losmandy_users] Re: Polar Alignment / Guiding Tracking



.









I used to just use the polar scope and then check tracking to Make sure my Y drift wasn't too bad. Now I use PemPro's Polar alignment tool which can sniff out polar misalignment within 1 arc minute in each axis. It still takes half an hour to do a good drift but the effort pays off.



Love ccdware stuff!



--- In Losmandy_users@yahoogroups.com , "d_kodama" kodama@...> wrote:

>

> Jerry,

>

> I do drift alignment first. Or you can use the iterative Gemini procedures to align.

>

> Either way, for accurate tracking for long exposures, you want to set your mount's altitude and azimuth adjustment accurately *first*. Then do your modeling, which is used for go-to slews.

>

> When doing your modeling for the first time, you first want to power up in the counterweight-down position with a cold-start. This is so the Gemini knows where the mount is positioned physically to start. It's important to start up properly so the slews don't cause the mount to go past the safety limits. After this is done, you never should release the clutches.

>

> The modeling is done by letting the Gemini slew to the selected alignment stars. Assuming you have set the correct time and other mount parameters, it should slew fairly close to the first alignment star you select, then you use the paddle to tweak the position in your scope (i.e. not by releasing the clutches). Subsequent alignment stars are handled the same way and you should find the Gemini slews getting closer and closer to being right on target.

>

> If I'm just going to be doing long exposures and not requiring a lot of accurate slewing (e.g. for a night of widefield shots), after polar axis alignment, I just use one star or just a small handful for the model (after clearing out any old model remaining in memory).

>

> Dave

>

>

> --- In Losmandy_users@yahoogroups.com , "ott_je" jc.ott@> wrote:

> >

> >

> > Dave,

> >

> > I pretty new to using my new GM-8 with Gemini. I see from your post below that you use drift alignment for Astrophotography. I've been attempting to find out the procedures, step-by-step, that are necessaary to drift align my system.

> >

> > Questions I have are whether or not to do modeling, etc prior to drift alignment?? Do you slew the scope to alignment stars or can one simply use the clutches to get the scope close and then slew to get the star centered??

> >

> > Anyway, I really need some help with this deal as I'm interested in fairly long exposure periods without error.

> >

> > Thanks,

> > Jerry.

> >

> >

> > --- In Losmandy_users@yahoogroups.com , "Dave Kodama" kodama@> wrote:

> > >

> > > Rod,

> > >

> > > Sounds like you're on the right path. Since you're using autoguiding,

> > > there's no reason to mess with Adaptive King or anything but sidereal

> > > rate.

> > >

> > > The only thing I might suggest is to use the Gemini polar axis

> > > correction routine rather than just depend on the error numbers

> > > resulting from running the modeling procedure (I haven't used it

> > > seriously myself except to try it as I use drift alignment normally).

> > >

> > > Dave

> > >

> > >

> > >

> > > --- In Losmandy_users@yahoogroups.com , Rod Mckay rodnscope@> wrote:

> > > >

> > > > Thanks Guys.

> > > >

> > > > I do see a little bit of field rotation, but it generally manifests

> > > as 0.01 degrees per 2 or 3 10 minute exposures, so isn't too bad.. The

> > > equipment I'm imaging with is a WO FLT110 refractor and modified Canon

> > > 350D DSLR, guided through a WO ZS66SD with Imaging Source DMK21 USB

> > > camera via GuideMaster software.. I have more of an issue with

> > > differential flexure, which I've managed to substantially reduce, and

> > > suspect the remaining 1-2 pixel drift per 10 min expsoure may be the

> > > FLT110 focuser sagging slightly, as I'm running out of other options.

> > > >

> > > > To date I've been relying on Gemini to tell me the polar alignment

> > > error, as it does after you've aligned the 3rd and subsequent stars..

> > > I then tweak alt & az, cold reset the mount, and start again - to

> > > hopefully observer a smaller error.. My observing position is kind of

> > > limited, and drift alignment is a bit tricky from there. - my view

> > > East is blocked by our house, and my wife's 2+m Jeruslem Artichokes

> > > currently obscure the view to the West, so my view is largely "Up",

> > > which is fine for imaging as I can usually get 3+hrs of imaging in for

> > > most objects if I catch them when they're just prior to straight up

> > > (ie. mount just rotated past the verticle).. Visually I'm as "on the

> > > pole" as I could be when I look through the scope, but that makes no

> > > allowance for less than perfect mounting which is bound to be the case.

> > > >

> > > > While I've got a pier, it's the only bit that's permanent - the rest

> > > of my kit comes in every night.. It was my hope that once I got

> > > alignment good, and assuming alt and az is well locked down, I should

> > > be able to get repeatably close enough by just taking the mount out

> > > and plonking it down on the MA adapter.. This seems to be the case,

> > > but is one reason I have yet to get fussy about perfect alignment.

> > > >

> > > > So, the plan looks like it should be to continue to chip away at

> > > better alignment but to not get too worried about being perfect.. Also

> > > not to worry about using Adaptive King.

> > > >

> > > > Cheers & thanks,

> > > > Rod

> > > >

> > > >

> > > >

> > > >

> > > >

---------------

> > > > From: Dave Kodama kodama@>

> > > > To: Losmandy_users@yahoogroups.com

> > > > Sent: Friday, 20 February, 2009 8:09:14 PM

> > > > Subject: [Losmandy_users] Re: Polar Alignment / Guiding Tracking

> > > >

> > > >

> > > > Greg,

> > > >

> > > > Sorry, I should have checked the manual first. I think you're

> > > > referring to "closed loop" tracking. This is OK for visual use but

> > > > being misaligned will still result in field rotation. Also, tracking

> > > > in the DEC axis will start to cause PE errors from that axis to

> > > > complicate the tracking errors.

> > > >

> > > > Anyway, going back to the question of how good your polar alignment

> > > > has to be... how much rotation you can tolerate in a photo depends on

> > > > all the factors I mentioned earlier, so it's really not possible to

> > > > give one number which is good enough for all imaging setups. Shooting

> > > > 4x5 film photos requires much, much more accurate alignment than

> > > > 2-minute sub-exposures with an APS-sized DSLR sensor.

> > > >

> > > > Dave

> > > >

> > > > --- In Losmandy_users@ yahoogroups. com, "Dave Kodama" kodama@> wrote:

> > > > >

> > > > > Greg,

> > > > >

> > > > > Aside from tweaking the tracking rate constants or periodic error

> > > > > correction which are RA-axis-only adjustments, I was not aware of any

> > > > > kind of tracking compensation that is done based on computed polar

> > > > > misalignment. For this to work, the mount would have to move in both

> > > > > RA and DEC. Can you explain the tracking error compensation you're

> > > > > referring to?

> > > > >

> > > > > Dave

> > > > >

> > > > >

> > > > > --- In Losmandy_users@ yahoogroups. com, "gnowellsct" tim71pos@>

> > > wrote:

> > > > > >

> > > > > > Actually Gemini has a tracking error compensation so the below is

> > > > > not strictly speaking

> > > > > > true. For shorter exposures, I'd guess five to ten minutes, a

> > > > > "kinda oK aligned scope" say

> > > > > > to within 15 arc minutes of the pole may not show that much field

> > > > > rotation to merit

> > > > > > zeroing in on the polar alignment.

> > > > > >

> > > > > > Wiser heads than me may have some views on that. But basically once

> > > > > the tracking is

> > > > > > working with a polar aligment compensation the only remaining issue

> > > > > is field rotation.

> > > > > > While field rortation is a big deal if you are using an alt-az mount

> > > > > without a wedge, once

> > > > > > you have gotten "pretty durn close" to polar aligned and have drift

> > > > > correction (like Gemini)

> > > > > > I don't think there'd be much need for a precise polar alignment

> > > > > except on real long

> > > > > > exposure work.

> > > > > >

> > > > > > maybe someone here can elaborate... .

> > > > > >

> > > > > > regards

> > > > > > Greg N

> > > > > >

> > > > > > --- In Losmandy_users@ yahoogroups. com, "Dave Kodama" kodama@>

> > > wrote:

> > > > > > >

> > > > > > > Rod,

> > > > > > >

> > > > > > > It's often a confusing issue, but the modeling (using lots of

> > > stars)

> > > > > > > is for go-to slewing accuracy and not tracking.

> > > > > > >

> > > > > > > If you want accurate tracking, you need to worry about polar

> > > > > > > alignment. How close it needs to be depends on your imaging

> > > > > > > requirements (how big your camera FOV is, how good your

> > > resolution,

> > > > > > > how long single exposures will be, etc.) I suggest aligning as

> > > well

> > > > > > > as you guess you need it to be, then do some test exposures and

> > > > see if

> > > > > > > you get field rotation in your shots. I think a lot of people

> > > sweat

> > > > > > > about really precise polar alignment without needing to.

> > > > > > >

> > > > > > > If you are guiding (i.e. using an autoguider or manually

> > > guiding the

> > > > > > > old way with an eyepiece), then the tracking rate you choose

> > > doesn't

> > > > > > > matter since the guiding will actively correct the mount's

> > > > tracking.

> > > > > > > So I just leave my mount set to sidereal tracking rate. The other

> > > > > > > tracking rates, including lunar and solar) are most useful in

> > > cases

> > > > > > > where you are *not* guiding like for visual use or say,

> > > > photographing

> > > > > > > a solar eclipse sequence.

> > > > > > >

> > > > > > > It's interesting that you found some odd interaction between the

> > > > King

> > > > > > > rate and the mount modeling, but I think that's not important.

> > > Just

> > > > > > > set it up using sidereal rate, then switch once you're done

> > > building

> > > > > > > the model. And as I said earlier, if you're guiding, just

> > > leave the

> > > > > > > mount in sidereal mode.

> > > > > > >

> > > > > > > Dave Kodama

> > > > > > >

> > > > > > >

> > > > > > > --- In Losmandy_users@ yahoogroups. com, Rod Mckay

> > > rodnscope@> wrote:

> > > > > > > >

> > > > > > > >

> > > > > > > > Hi,

> > > > > > > >

> > > > > > > > Couple of quesitons to the Guru's out there...

> > > > > > > >

> > > > > > > > 1. How close do people generally get their polar alignment in

> > > > > > > permanent installations? I'm in the process of setting up a

> > > > pier and

> > > > > > > can plonk the mount on and be within ~7' of the pole - is that

> > > > > > > reasonable, or should I spend more time trying to hone in closer?

> > > > > > > When adding more stars to the model it seems that the error jumps

> > > > > > > around by a few mninutes, so will I end up chasing my tail?

> > > > > > > >

> > > > > > > > I've previously tried using the Gemini polar alignment tools

> > > with

> > > > > > > varied success - it seems hit or miss whether you end up closer or

> > > > > not.

> > > > > > > >

> > > > > > > > 2. When auto guiding, do people generally have the mount set for

> > > > > > > Siderial or Adaptive King?

> > > > > > > >

> > > > > > > > 3. Is if odd that when using Siderial and doing a series of

> > > > > > > alignments I get a reported polar alignment error of ~ 7' on each

> > > > > > > axis, but when I do a number of alignments when set to Adaptive

> > > > King I

> > > > > > > get a reported polar alignment error of 30+' in each axis? I

> > > didn't

> > > > > > > touch the alt or az between alignments. Should I align on Siderial

> > > > > > > and then switch to Adaptive King?

> > > > > > > >

> > > > > > > > I'm sure I'll sort all this out in time, but I'd be

> > > interested to

> > > > > > > know if anyone has the answers.

> > > > > > > >

> > > > > > > > Cheers & thanks,

> > > > > > > > Rod

> > > > > > > >

> > > > > > > >

> > > > > > > > Make Yahoo!7 your homepage and win a trip to the Quiksilver

> > > > > > > Pro. Find out more

> > > > > > > >

> > > > > > >

> > > > > >

> > > > >

> > > >

> > > >

> > > >

> > > >

> > > >

> > > > Stay connected to the people that matter most with a smarter

> > > inbox. Take a look au.docs.yahoo.com/mail/smarterinbox

> > > >

> > > > [Non-text portions of this message have been removed]

> > > >

> > >

> >

>









[Non-text portions of this message have been removed]







----------------------------

#43841 Sep 2, 2009

Make sure you set it to ALL SPEEDS and see if it moves then.

Floyd --- In Losmandy_users@yahoogroups.com, Gjanek@... wrote:

>

>

>

> I just recently purchased a Gemini Losmandy mount. I do all the procedures that you describe. I slew to the first star, it is just on the edge of the FOV. My problem is centering the star. I went back and checked the manual, and it said to use the buttons RA+- or Dec+- to center the star. When I do this the mount will not move. What I'm I missing?

>

>

>

> Gil

>

>

> ----- Original Message -----

> From: "tpiccian" tpicciani@...>

> To: "Losmandy users" Losmandy_users@yahoogroups.com>

> Sent: Wednesday, September 2, 2009 11:52:13 AM GMT -05:00 US/Canada Eastern

> Subject: [Losmandy_users] Re: Polar Alignment / Guiding Tracking

>

> ..

>

>

>

>

> I used to just use the polar scope and then check tracking to Make sure my Y drift wasn't too bad. Now I use PemPro's Polar alignment tool which can sniff out polar misalignment within 1 arc minute in each axis. It still takes half an hour to do a good drift but the effort pays off.

>

> Love ccdware stuff!

>

> --- In Losmandy_users@yahoogroups.com , "d_kodama" kodama@> wrote:

> >

> > Jerry,

> >

> > I do drift alignment first. Or you can use the iterative Gemini procedures to align.

> >

> > Either way, for accurate tracking for long exposures, you want to set your mount's altitude and azimuth adjustment accurately *first*. Then do your modeling, which is used for go-to slews.

> >

> > When doing your modeling for the first time, you first want to power up in the counterweight-down position with a cold-start. This is so the Gemini knows where the mount is positioned physically to start. It's important to start up properly so the slews don't cause the mount to go past the safety limits. After this is done, you never should release the clutches.

> >

> > The modeling is done by letting the Gemini slew to the selected alignment stars. Assuming you have set the correct time and other mount parameters, it should slew fairly close to the first alignment star you select, then you use the paddle to tweak the position in your scope (i.e. not by releasing the clutches). Subsequent alignment stars are handled the same way and you should find the Gemini slews getting closer and closer to being right on target.

> >

> > If I'm just going to be doing long exposures and not requiring a lot of accurate slewing (e.g. for a night of widefield shots), after polar axis alignment, I just use one star or just a small handful for the model (after clearing out any old model remaining in memory).

> >

> > Dave

> >

> >

> > --- In Losmandy_users@yahoogroups.com , "ott_je" jc.ott@> wrote:

> > >

> > >

> > > Dave,

> > >

> > > I pretty new to using my new GM-8 with Gemini. I see from your post below that you use drift alignment for Astrophotography. I've been attempting to find out the procedures, step-by-step, that are necessaary to drift align my system.

> > >

> > > Questions I have are whether or not to do modeling, etc prior to drift alignment?? Do you slew the scope to alignment stars or can one simply use the clutches to get the scope close and then slew to get the star centered??

> > >

> > > Anyway, I really need some help with this deal as I'm interested in fairly long exposure periods without error.

> > >

> > > Thanks,

> > > Jerry.

> > >

> > >

> > > --- In Losmandy_users@yahoogroups.com , "Dave Kodama" kodama@> wrote:

> > > >

> > > > Rod,

> > > >

> > > > Sounds like you're on the right path. Since you're using autoguiding,

> > > > there's no reason to mess with Adaptive King or anything but sidereal

> > > > rate.

> > > >

> > > > The only thing I might suggest is to use the Gemini polar axis

> > > > correction routine rather than just depend on the error numbers

> > > > resulting from running the modeling procedure (I haven't used it

> > > > seriously myself except to try it as I use drift alignment normally).

> > > >

> > > > Dave

> > > >

> > > >

> > > >

> > > > --- In Losmandy_users@yahoogroups.com , Rod Mckay rodnscope@> wrote:

> > > > >

> > > > > Thanks Guys.

> > > > >

> > > > > I do see a little bit of field rotation, but it generally manifests

> > > > as 0.01 degrees per 2 or 3 10 minute exposures, so isn't too bad... The

> > > > equipment I'm imaging with is a WO FLT110 refractor and modified Canon

> > > > 350D DSLR, guided through a WO ZS66SD with Imaging Source DMK21 USB

> > > > camera via GuideMaster software... I have more of an issue with

> > > > differential flexure, which I've managed to substantially reduce, and

> > > > suspect the remaining 1-2 pixel drift per 10 min expsoure may be the

> > > > FLT110 focuser sagging slightly, as I'm running out of other options.

> > > > >

> > > > > To date I've been relying on Gemini to tell me the polar alignment

> > > > error, as it does after you've aligned the 3rd and subsequent stars...

> > > > I then tweak alt & az, cold reset the mount, and start again - to

> > > > hopefully observer a smaller error... My observing position is kind of

> > > > limited, and drift alignment is a bit tricky from there.. - my view

> > > > East is blocked by our house, and my wife's 2+m Jeruslem Artichokes

> > > > currently obscure the view to the West, so my view is largely "Up",

> > > > which is fine for imaging as I can usually get 3+hrs of imaging in for

> > > > most objects if I catch them when they're just prior to straight up

> > > > (ie. mount just rotated past the verticle)... Visually I'm as "on the

> > > > pole" as I could be when I look through the scope, but that makes no

> > > > allowance for less than perfect mounting which is bound to be the case.

> > > > >

> > > > > While I've got a pier, it's the only bit that's permanent - the rest

> > > > of my kit comes in every night... It was my hope that once I got

> > > > alignment good, and assuming alt and az is well locked down, I should

> > > > be able to get repeatably close enough by just taking the mount out

> > > > and plonking it down on the MA adapter... This seems to be the case,

> > > > but is one reason I have yet to get fussy about perfect alignment.

> > > > >

> > > > > So, the plan looks like it should be to continue to chip away at

> > > > better alignment but to not get too worried about being perfect... Also

> > > > not to worry about using Adaptive King.

> > > > >

> > > > > Cheers & thanks,

> > > > > Rod

> > > > >

> > > > >

> > > > >

> > > > >

> > > > >

---------------

> > > > > From: Dave Kodama kodama@>

> > > > > To: Losmandy_users@yahoogroups.com

> > > > > Sent: Friday, 20 February, 2009 8:09:14 PM

> > > > > Subject: [Losmandy_users] Re: Polar Alignment / Guiding Tracking

> > > > >

> > > > >

> > > > > Greg,

> > > > >

> > > > > Sorry, I should have checked the manual first. I think you're

> > > > > referring to "closed loop" tracking. This is OK for visual use but

> > > > > being misaligned will still result in field rotation. Also, tracking

> > > > > in the DEC axis will start to cause PE errors from that axis to

> > > > > complicate the tracking errors.

> > > > >

> > > > > Anyway, going back to the question of how good your polar alignment

> > > > > has to be... how much rotation you can tolerate in a photo depends on

> > > > > all the factors I mentioned earlier, so it's really not possible to

> > > > > give one number which is good enough for all imaging setups. Shooting

> > > > > 4x5 film photos requires much, much more accurate alignment than

> > > > > 2-minute sub-exposures with an APS-sized DSLR sensor.

> > > > >

> > > > > Dave

> > > > >

> > > > > --- In Losmandy_users@ yahoogroups. com, "Dave Kodama" kodama@> wrote:

> > > > > >

> > > > > > Greg,

> > > > > >

> > > > > > Aside from tweaking the tracking rate constants or periodic error

> > > > > > correction which are RA-axis-only adjustments, I was not aware of any

> > > > > > kind of tracking compensation that is done based on computed polar

> > > > > > misalignment. For this to work, the mount would have to move in both

> > > > > > RA and DEC. Can you explain the tracking error compensation you're

> > > > > > referring to?

> > > > > >

> > > > > > Dave

> > > > > >

> > > > > >

> > > > > > --- In Losmandy_users@ yahoogroups. com, "gnowellsct" tim71pos@>

> > > > wrote:

> > > > > > >

> > > > > > > Actually Gemini has a tracking error compensation so the below is

> > > > > > not strictly speaking

> > > > > > > true. For shorter exposures, I'd guess five to ten minutes, a

> > > > > > "kinda oK aligned scope" say

> > > > > > > to within 15 arc minutes of the pole may not show that much field

> > > > > > rotation to merit

> > > > > > > zeroing in on the polar alignment.

> > > > > > >

> > > > > > > Wiser heads than me may have some views on that. But basically once

> > > > > > the tracking is

> > > > > > > working with a polar aligment compensation the only remaining issue

> > > > > > is field rotation.

> > > > > > > While field rortation is a big deal if you are using an alt-az mount

> > > > > > without a wedge, once

> > > > > > > you have gotten "pretty durn close" to polar aligned and have drift

> > > > > > correction (like Gemini)

> > > > > > > I don't think there'd be much need for a precise polar alignment

> > > > > > except on real long

> > > > > > > exposure work.

> > > > > > >

> > > > > > > maybe someone here can elaborate... .

> > > > > > >

> > > > > > > regards

> > > > > > > Greg N

> > > > > > >

> > > > > > > --- In Losmandy_users@ yahoogroups. com, "Dave Kodama" kodama@>

> > > > wrote:

> > > > > > > >

> > > > > > > > Rod,

> > > > > > > >

> > > > > > > > It's often a confusing issue, but the modeling (using lots of

> > > > stars)

> > > > > > > > is for go-to slewing accuracy and not tracking.

> > > > > > > >

> > > > > > > > If you want accurate tracking, you need to worry about polar

> > > > > > > > alignment. How close it needs to be depends on your imaging

> > > > > > > > requirements (how big your camera FOV is, how good your

> > > > resolution,

> > > > > > > > how long single exposures will be, etc.) I suggest aligning as

> > > > well

> > > > > > > > as you guess you need it to be, then do some test exposures and

> > > > > see if

> > > > > > > > you get field rotation in your shots. I think a lot of people

> > > > sweat

> > > > > > > > about really precise polar alignment without needing to.

> > > > > > > >

> > > > > > > > If you are guiding (i.e. using an autoguider or manually

> > > > guiding the

> > > > > > > > old way with an eyepiece), then the tracking rate you choose

> > > > doesn't

> > > > > > > > matter since the guiding will actively correct the mount's

> > > > > tracking.

> > > > > > > > So I just leave my mount set to sidereal tracking rate. The other

> > > > > > > > tracking rates, including lunar and solar) are most useful in

> > > > cases

> > > > > > > > where you are *not* guiding like for visual use or say,

> > > > > photographing

> > > > > > > > a solar eclipse sequence.

> > > > > > > >

> > > > > > > > It's interesting that you found some odd interaction between the

> > > > > King

> > > > > > > > rate and the mount modeling, but I think that's not important.

> > > > Just

> > > > > > > > set it up using sidereal rate, then switch once you're done

> > > > building

> > > > > > > > the model. And as I said earlier, if you're guiding, just

> > > > leave the

> > > > > > > > mount in sidereal mode.

> > > > > > > >

> > > > > > > > Dave Kodama

> > > > > > > >

> > > > > > > >

> > > > > > > > --- In Losmandy_users@ yahoogroups. com, Rod Mckay

> > > > rodnscope@> wrote:

> > > > > > > > >

> > > > > > > > >

> > > > > > > > > Hi,

> > > > > > > > >

> > > > > > > > > Couple of quesitons to the Guru's out there...

> > > > > > > > >

> > > > > > > > > 1. How close do people generally get their polar alignment in

> > > > > > > > permanent installations? I'm in the process of setting up a

> > > > > pier and

> > > > > > > > can plonk the mount on and be within ~7' of the pole - is that

> > > > > > > > reasonable, or should I spend more time trying to hone in closer?

> > > > > > > > When adding more stars to the model it seems that the error jumps

> > > > > > > > around by a few mninutes, so will I end up chasing my tail?

> > > > > > > > >

> > > > > > > > > I've previously tried using the Gemini polar alignment tools

> > > > with

> > > > > > > > varied success - it seems hit or miss whether you end up closer or

> > > > > > not.

> > > > > > > > >

> > > > > > > > > 2. When auto guiding, do people generally have the mount set for

> > > > > > > > Siderial or Adaptive King?

> > > > > > > > >

> > > > > > > > > 3. Is if odd that when using Siderial and doing a series of

> > > > > > > > alignments I get a reported polar alignment error of ~ 7' on each

> > > > > > > > axis, but when I do a number of alignments when set to Adaptive

> > > > > King I

> > > > > > > > get a reported polar alignment error of 30+' in each axis? I

> > > > didn't

> > > > > > > > touch the alt or az between alignments. Should I align on Siderial

> > > > > > > > and then switch to Adaptive King?

> > > > > > > > >

> > > > > > > > > I'm sure I'll sort all this out in time, but I'd be

> > > > interested to

> > > > > > > > know if anyone has the answers.

> > > > > > > > >

> > > > > > > > > Cheers & thanks,

> > > > > > > > > Rod

> > > > > > > > >

> > > > > > > > >

> > > > > > > > > Make Yahoo!7 your homepage and win a trip to the Quiksilver

> > > > > > > > Pro. Find out more

> > > > > > > > >

> > > > > > > >

> > > > > > >

> > > > > >

> > > > >

> > > > >

> > > > >

> > > > >

> > > > >

> > > > > Stay connected to the people that matter most with a smarter

> > > > inbox. Take a look au.docs.yahoo.com/mail/smarterinbox

> > > > >

> > > > > [Non-text portions of this message have been removed]

> > > > >

> > > >

> > >

> >

>

>

>

>

> [Non-text portions of this message have been removed]

>







----------------------------

#43843 Sep 2, 2009

Do you set that when you do cold start, or after you slew to an object?. Do set it in the hand control setup?

Gil





----- Original Message -----

From: "bakersfieldbiker" fblue@...>

To: "Losmandy users" Losmandy_users@yahoogroups.com>

Sent: Wednesday, September 2, 2009 3:38:07 PM GMT -05:00 US/Canada Eastern

Subject: [Losmandy_users] Re: Polar Alignment / Guiding Tracking



.









Make sure you set it to ALL SPEEDS and see if it moves then.

Floyd

--- In Losmandy_users@yahoogroups.com , Gjanek@... wrote:

>

>

>

> I just recently purchased a Gemini Losmandy mount. I do all the procedures that you describe. I slew to the first star, it is just on the edge of the FOV. My problem is centering the star. I went back and checked the manual, and it said to use the buttons RA+- or Dec+- to center the star. When I do this the mount will not move. What I'm I missing?

>

>

>

> Gil

>

>

> ----- Original Message -----

> From: "tpiccian" tpicciani@...>

> To: "Losmandy users" Losmandy_users@yahoogroups.com >

> Sent: Wednesday, September 2, 2009 11:52:13 AM GMT -05:00 US/Canada Eastern

> Subject: [Losmandy_users] Re: Polar Alignment / Guiding Tracking

>

> ..

>

>

>

>

> I used to just use the polar scope and then check tracking to Make sure my Y drift wasn't too bad. Now I use PemPro's Polar alignment tool which can sniff out polar misalignment within 1 arc minute in each axis. It still takes half an hour to do a good drift but the effort pays off.

>

> Love ccdware stuff!

>

> --- In Losmandy_users@yahoogroups.com , "d_kodama" kodama@> wrote:

> >

> > Jerry,

> >

> > I do drift alignment first. Or you can use the iterative Gemini procedures to align.

> >

> > Either way, for accurate tracking for long exposures, you want to set your mount's altitude and azimuth adjustment accurately *first*. Then do your modeling, which is used for go-to slews.

> >

> > When doing your modeling for the first time, you first want to power up in the counterweight-down position with a cold-start. This is so the Gemini knows where the mount is positioned physically to start. It's important to start up properly so the slews don't cause the mount to go past the safety limits. After this is done, you never should release the clutches.

> >

> > The modeling is done by letting the Gemini slew to the selected alignment stars. Assuming you have set the correct time and other mount parameters, it should slew fairly close to the first alignment star you select, then you use the paddle to tweak the position in your scope (i.e. not by releasing the clutches). Subsequent alignment stars are handled the same way and you should find the Gemini slews getting closer and closer to being right on target.

> >

> > If I'm just going to be doing long exposures and not requiring a lot of accurate slewing (e.g. for a night of widefield shots), after polar axis alignment, I just use one star or just a small handful for the model (after clearing out any old model remaining in memory).

> >

> > Dave

> >

> >

> > --- In Losmandy_users@yahoogroups.com , "ott_je" jc.ott@> wrote:

> > >

> > >

> > > Dave,

> > >

> > > I pretty new to using my new GM-8 with Gemini. I see from your post below that you use drift alignment for Astrophotography. I've been attempting to find out the procedures, step-by-step, that are necessaary to drift align my system.

> > >

> > > Questions I have are whether or not to do modeling, etc prior to drift alignment?? Do you slew the scope to alignment stars or can one simply use the clutches to get the scope close and then slew to get the star centered??

> > >

> > > Anyway, I really need some help with this deal as I'm interested in fairly long exposure periods without error.

> > >

> > > Thanks,

> > > Jerry.

> > >

> > >

> > > --- In Losmandy_users@yahoogroups.com , "Dave Kodama" kodama@> wrote:

> > > >

> > > > Rod,

> > > >

> > > > Sounds like you're on the right path. Since you're using autoguiding,

> > > > there's no reason to mess with Adaptive King or anything but sidereal

> > > > rate.

> > > >

> > > > The only thing I might suggest is to use the Gemini polar axis

> > > > correction routine rather than just depend on the error numbers

> > > > resulting from running the modeling procedure (I haven't used it

> > > > seriously myself except to try it as I use drift alignment normally).

> > > >

> > > > Dave

> > > >

> > > >

> > > >

> > > > --- In Losmandy_users@yahoogroups.com , Rod Mckay rodnscope@> wrote:

> > > > >

> > > > > Thanks Guys.

> > > > >

> > > > > I do see a little bit of field rotation, but it generally manifests

> > > > as 0.01 degrees per 2 or 3 10 minute exposures, so isn't too bad... The

> > > > equipment I'm imaging with is a WO FLT110 refractor and modified Canon

> > > > 350D DSLR, guided through a WO ZS66SD with Imaging Source DMK21 USB

> > > > camera via GuideMaster software... I have more of an issue with

> > > > differential flexure, which I've managed to substantially reduce, and

> > > > suspect the remaining 1-2 pixel drift per 10 min expsoure may be the

> > > > FLT110 focuser sagging slightly, as I'm running out of other options.

> > > > >

> > > > > To date I've been relying on Gemini to tell me the polar alignment

> > > > error, as it does after you've aligned the 3rd and subsequent stars...

> > > > I then tweak alt & az, cold reset the mount, and start again - to

> > > > hopefully observer a smaller error... My observing position is kind of

> > > > limited, and drift alignment is a bit tricky from there.. - my view

> > > > East is blocked by our house, and my wife's 2+m Jeruslem Artichokes

> > > > currently obscure the view to the West, so my view is largely "Up",

> > > > which is fine for imaging as I can usually get 3+hrs of imaging in for

> > > > most objects if I catch them when they're just prior to straight up

> > > > (ie. mount just rotated past the verticle)... Visually I'm as "on the

> > > > pole" as I could be when I look through the scope, but that makes no

> > > > allowance for less than perfect mounting which is bound to be the case.

> > > > >

> > > > > While I've got a pier, it's the only bit that's permanent - the rest

> > > > of my kit comes in every night... It was my hope that once I got

> > > > alignment good, and assuming alt and az is well locked down, I should

> > > > be able to get repeatably close enough by just taking the mount out

> > > > and plonking it down on the MA adapter... This seems to be the case,

> > > > but is one reason I have yet to get fussy about perfect alignment.

> > > > >

> > > > > So, the plan looks like it should be to continue to chip away at

> > > > better alignment but to not get too worried about being perfect... Also

> > > > not to worry about using Adaptive King.

> > > > >

> > > > > Cheers & thanks,

> > > > > Rod

> > > > >

> > > > >

> > > > >

> > > > >

> > > > >

---------------

> > > > > From: Dave Kodama kodama@>

> > > > > To: Losmandy_users@yahoogroups.com

> > > > > Sent: Friday, 20 February, 2009 8:09:14 PM

> > > > > Subject: [Losmandy_users] Re: Polar Alignment / Guiding Tracking

> > > > >

> > > > >

> > > > > Greg,

> > > > >

> > > > > Sorry, I should have checked the manual first. I think you're

> > > > > referring to "closed loop" tracking. This is OK for visual use but

> > > > > being misaligned will still result in field rotation. Also, tracking

> > > > > in the DEC axis will start to cause PE errors from that axis to

> > > > > complicate the tracking errors.

> > > > >

> > > > > Anyway, going back to the question of how good your polar alignment

> > > > > has to be... how much rotation you can tolerate in a photo depends on

> > > > > all the factors I mentioned earlier, so it's really not possible to

> > > > > give one number which is good enough for all imaging setups. Shooting

> > > > > 4x5 film photos requires much, much more accurate alignment than

> > > > > 2-minute sub-exposures with an APS-sized DSLR sensor.

> > > > >

> > > > > Dave

> > > > >

> > > > > --- In Losmandy_users@ yahoogroups. com, "Dave Kodama" kodama@> wrote:

> > > > > >

> > > > > > Greg,

> > > > > >

> > > > > > Aside from tweaking the tracking rate constants or periodic error

> > > > > > correction which are RA-axis-only adjustments, I was not aware of any

> > > > > > kind of tracking compensation that is done based on computed polar

> > > > > > misalignment. For this to work, the mount would have to move in both

> > > > > > RA and DEC. Can you explain the tracking error compensation you're

> > > > > > referring to?

> > > > > >

> > > > > > Dave

> > > > > >

> > > > > >

> > > > > > --- In Losmandy_users@ yahoogroups. com, "gnowellsct" tim71pos@>

> > > > wrote:

> > > > > > >

> > > > > > > Actually Gemini has a tracking error compensation so the below is

> > > > > > not strictly speaking

> > > > > > > true. For shorter exposures, I'd guess five to ten minutes, a

> > > > > > "kinda oK aligned scope" say

> > > > > > > to within 15 arc minutes of the pole may not show that much field

> > > > > > rotation to merit

> > > > > > > zeroing in on the polar alignment.

> > > > > > >

> > > > > > > Wiser heads than me may have some views on that. But basically once

> > > > > > the tracking is

> > > > > > > working with a polar aligment compensation the only remaining issue

> > > > > > is field rotation.

> > > > > > > While field rortation is a big deal if you are using an alt-az mount

> > > > > > without a wedge, once

> > > > > > > you have gotten "pretty durn close" to polar aligned and have drift

> > > > > > correction (like Gemini)

> > > > > > > I don't think there'd be much need for a precise polar alignment

> > > > > > except on real long

> > > > > > > exposure work.

> > > > > > >

> > > > > > > maybe someone here can elaborate... .

> > > > > > >

> > > > > > > regards

> > > > > > > Greg N

> > > > > > >

> > > > > > > --- In Losmandy_users@ yahoogroups. com, "Dave Kodama" kodama@>

> > > > wrote:

> > > > > > > >

> > > > > > > > Rod,

> > > > > > > >

> > > > > > > > It's often a confusing issue, but the modeling (using lots of

> > > > stars)

> > > > > > > > is for go-to slewing accuracy and not tracking.

> > > > > > > >

> > > > > > > > If you want accurate tracking, you need to worry about polar

> > > > > > > > alignment. How close it needs to be depends on your imaging

> > > > > > > > requirements (how big your camera FOV is, how good your

> > > > resolution,

> > > > > > > > how long single exposures will be, etc.) I suggest aligning as

> > > > well

> > > > > > > > as you guess you need it to be, then do some test exposures and

> > > > > see if

> > > > > > > > you get field rotation in your shots. I think a lot of people

> > > > sweat

> > > > > > > > about really precise polar alignment without needing to.

> > > > > > > >

> > > > > > > > If you are guiding (i.e. using an autoguider or manually

> > > > guiding the

> > > > > > > > old way with an eyepiece), then the tracking rate you choose

> > > > doesn't

> > > > > > > > matter since the guiding will actively correct the mount's

> > > > > tracking.

> > > > > > > > So I just leave my mount set to sidereal tracking rate. The other

> > > > > > > > tracking rates, including lunar and solar) are most useful in

> > > > cases

> > > > > > > > where you are *not* guiding like for visual use or say,

> > > > > photographing

> > > > > > > > a solar eclipse sequence.

> > > > > > > >

> > > > > > > > It's interesting that you found some odd interaction between the

> > > > > King

> > > > > > > > rate and the mount modeling, but I think that's not important.

> > > > Just

> > > > > > > > set it up using sidereal rate, then switch once you're done

> > > > building

> > > > > > > > the model. And as I said earlier, if you're guiding, just

> > > > leave the

> > > > > > > > mount in sidereal mode.

> > > > > > > >

> > > > > > > > Dave Kodama

> > > > > > > >

> > > > > > > >

> > > > > > > > --- In Losmandy_users@ yahoogroups. com, Rod Mckay

> > > > rodnscope@> wrote:

> > > > > > > > >

> > > > > > > > >

> > > > > > > > > Hi,

> > > > > > > > >

> > > > > > > > > Couple of quesitons to the Guru's out there...

> > > > > > > > >

> > > > > > > > > 1. How close do people generally get their polar alignment in

> > > > > > > > permanent installations? I'm in the process of setting up a

> > > > > pier and

> > > > > > > > can plonk the mount on and be within ~7' of the pole - is that

> > > > > > > > reasonable, or should I spend more time trying to hone in closer?

> > > > > > > > When adding more stars to the model it seems that the error jumps

> > > > > > > > around by a few mninutes, so will I end up chasing my tail?

> > > > > > > > >

> > > > > > > > > I've previously tried using the Gemini polar alignment tools

> > > > with

> > > > > > > > varied success - it seems hit or miss whether you end up closer or

> > > > > > not.

> > > > > > > > >

> > > > > > > > > 2. When auto guiding, do people generally have the mount set for

> > > > > > > > Siderial or Adaptive King?

> > > > > > > > >

> > > > > > > > > 3. Is if odd that when using Siderial and doing a series of

> > > > > > > > alignments I get a reported polar alignment error of ~ 7' on each

> > > > > > > > axis, but when I do a number of alignments when set to Adaptive

> > > > > King I

> > > > > > > > get a reported polar alignment error of 30+' in each axis? I

> > > > didn't

> > > > > > > > touch the alt or az between alignments. Should I align on Siderial

> > > > > > > > and then switch to Adaptive King?

> > > > > > > > >

> > > > > > > > > I'm sure I'll sort all this out in time, but I'd be

> > > > interested to

> > > > > > > > know if anyone has the answers.

> > > > > > > > >

> > > > > > > > > Cheers & thanks,

> > > > > > > > > Rod

> > > > > > > > >

> > > > > > > > >

> > > > > > > > > Make Yahoo!7 your homepage and win a trip to the Quiksilver

> > > > > > > > Pro. Find out more

> > > > > > > > >

> > > > > > > >

> > > > > > >

> > > > > >

> > > > >

> > > > >

> > > > >

> > > > >

> > > > >

> > > > > Stay connected to the people that matter most with a smarter

> > > > inbox. Take a look au.docs.yahoo.com/mail/smarterinbox

> > > > >

> > > > > [Non-text portions of this message have been removed]

> > > > >

> > > >

> > >

> >

>

>

>

>

> [Non-text portions of this message have been removed]

>









[Non-text portions of this message have been removed]







----------------------------

#43846 Sep 2, 2009

Thanks for the reply Dave and others,



I'm fairly well versed in the mount setup with leveling, using the Polar Alignment Scope, Counter Weight Down (except that I've had issues with getting the CWD really set accurately so if anyone has any tips on this one I'd welcome them), startup, doing a syncronize, additional aligns, and the Polar Axis Correction function.



So, I'm still a bit confused about where I go from there and how I should proceed to do an accurate two star drift alignment. I'm still not clear on whether the modeling or the drift alignment comes first???



You mention that I should not release the clutches so should I goto particular alignment stars to get started with the drift align??



And, after the drift align is done, will the mount do accurate goto's? In other words, is the modeling preserved?



Thanks and sorry for the confusion. I've seen and read so many examples on the Internet that my head is spinning. I appreciate yours and anyone else's help with this matter.



Best regards,

Jerry.











--- In Losmandy_users@yahoogroups.com, "d_kodama" kodama@...> wrote:

>

> Jerry,

>

> I do drift alignment first. Or you can use the iterative Gemini procedures to align.

>

> Either way, for accurate tracking for long exposures, you want to set your mount's altitude and azimuth adjustment accurately *first*. Then do your modeling, which is used for go-to slews.

>

> When doing your modeling for the first time, you first want to power up in the counterweight-down position with a cold-start. This is so the Gemini knows where the mount is positioned physically to start. It's important to start up properly so the slews don't cause the mount to go past the safety limits. After this is done, you never should release the clutches.

>

> The modeling is done by letting the Gemini slew to the selected alignment stars. Assuming you have set the correct time and other mount parameters, it should slew fairly close to the first alignment star you select, then you use the paddle to tweak the position in your scope (i.e. not by releasing the clutches). Subsequent alignment stars are handled the same way and you should find the Gemini slews getting closer and closer to being right on target.

>

> If I'm just going to be doing long exposures and not requiring a lot of accurate slewing (e.g. for a night of widefield shots), after polar axis alignment, I just use one star or just a small handful for the model (after clearing out any old model remaining in memory).

>

> Dave

>

>

> --- In Losmandy_users@yahoogroups.com, "ott_je" jc.ott@> wrote:

> >

> >

> > Dave,

> >

> > I pretty new to using my new GM-8 with Gemini. I see from your post below that you use drift alignment for Astrophotography. I've been attempting to find out the procedures, step-by-step, that are necessaary to drift align my system.

> >

> > Questions I have are whether or not to do modeling, etc prior to drift alignment?? Do you slew the scope to alignment stars or can one simply use the clutches to get the scope close and then slew to get the star centered??

> >

> > Anyway, I really need some help with this deal as I'm interested in fairly long exposure periods without error.

> >

> > Thanks,

> > Jerry.

> >

> >

> > --- In Losmandy_users@yahoogroups.com, "Dave Kodama" kodama@> wrote:

> > >

> > > Rod,

> > >

> > > Sounds like you're on the right path. Since you're using autoguiding,

> > > there's no reason to mess with Adaptive King or anything but sidereal

> > > rate.

> > >

> > > The only thing I might suggest is to use the Gemini polar axis

> > > correction routine rather than just depend on the error numbers

> > > resulting from running the modeling procedure (I haven't used it

> > > seriously myself except to try it as I use drift alignment normally).

> > >

> > > Dave

> > >

> > >

> > >

> > > --- In Losmandy_users@yahoogroups.com, Rod Mckay rodnscope@> wrote:

> > > >

> > > > Thanks Guys.

> > > >

> > > > I do see a little bit of field rotation, but it generally manifests

> > > as 0.01 degrees per 2 or 3 10 minute exposures, so isn't too bad.. The

> > > equipment I'm imaging with is a WO FLT110 refractor and modified Canon

> > > 350D DSLR, guided through a WO ZS66SD with Imaging Source DMK21 USB

> > > camera via GuideMaster software.. I have more of an issue with

> > > differential flexure, which I've managed to substantially reduce, and

> > > suspect the remaining 1-2 pixel drift per 10 min expsoure may be the

> > > FLT110 focuser sagging slightly, as I'm running out of other options.

> > > >

> > > > To date I've been relying on Gemini to tell me the polar alignment

> > > error, as it does after you've aligned the 3rd and subsequent stars..

> > > I then tweak alt & az, cold reset the mount, and start again - to

> > > hopefully observer a smaller error.. My observing position is kind of

> > > limited, and drift alignment is a bit tricky from there. - my view

> > > East is blocked by our house, and my wife's 2+m Jeruslem Artichokes

> > > currently obscure the view to the West, so my view is largely "Up",

> > > which is fine for imaging as I can usually get 3+hrs of imaging in for

> > > most objects if I catch them when they're just prior to straight up

> > > (ie. mount just rotated past the verticle).. Visually I'm as "on the

> > > pole" as I could be when I look through the scope, but that makes no

> > > allowance for less than perfect mounting which is bound to be the case.

> > > >

> > > > While I've got a pier, it's the only bit that's permanent - the rest

> > > of my kit comes in every night.. It was my hope that once I got

> > > alignment good, and assuming alt and az is well locked down, I should

> > > be able to get repeatably close enough by just taking the mount out

> > > and plonking it down on the MA adapter.. This seems to be the case,

> > > but is one reason I have yet to get fussy about perfect alignment.

> > > >

> > > > So, the plan looks like it should be to continue to chip away at

> > > better alignment but to not get too worried about being perfect.. Also

> > > not to worry about using Adaptive King.

> > > >

> > > > Cheers & thanks,

> > > > Rod

> > > >

> > > >

> > > >

> > > >

> > > >

---------------

> > > > From: Dave Kodama kodama@>

> > > > To: Losmandy_users@yahoogroups.com

> > > > Sent: Friday, 20 February, 2009 8:09:14 PM

> > > > Subject: [Losmandy_users] Re: Polar Alignment / Guiding Tracking

> > > >

> > > >

> > > > Greg,

> > > >

> > > > Sorry, I should have checked the manual first. I think you're

> > > > referring to "closed loop" tracking. This is OK for visual use but

> > > > being misaligned will still result in field rotation. Also, tracking

> > > > in the DEC axis will start to cause PE errors from that axis to

> > > > complicate the tracking errors.

> > > >

> > > > Anyway, going back to the question of how good your polar alignment

> > > > has to be... how much rotation you can tolerate in a photo depends on

> > > > all the factors I mentioned earlier, so it's really not possible to

> > > > give one number which is good enough for all imaging setups. Shooting

> > > > 4x5 film photos requires much, much more accurate alignment than

> > > > 2-minute sub-exposures with an APS-sized DSLR sensor.

> > > >

> > > > Dave

> > > >

> > > > --- In Losmandy_users@ yahoogroups. com, "Dave Kodama" kodama@> wrote:

> > > > >

> > > > > Greg,

> > > > >

> > > > > Aside from tweaking the tracking rate constants or periodic error

> > > > > correction which are RA-axis-only adjustments, I was not aware of any

> > > > > kind of tracking compensation that is done based on computed polar

> > > > > misalignment. For this to work, the mount would have to move in both

> > > > > RA and DEC. Can you explain the tracking error compensation you're

> > > > > referring to?

> > > > >

> > > > > Dave

> > > > >

> > > > >

> > > > > --- In Losmandy_users@ yahoogroups. com, "gnowellsct" tim71pos@>

> > > wrote:

> > > > > >

> > > > > > Actually Gemini has a tracking error compensation so the below is

> > > > > not strictly speaking

> > > > > > true. For shorter exposures, I'd guess five to ten minutes, a

> > > > > "kinda oK aligned scope" say

> > > > > > to within 15 arc minutes of the pole may not show that much field

> > > > > rotation to merit

> > > > > > zeroing in on the polar alignment.

> > > > > >

> > > > > > Wiser heads than me may have some views on that. But basically once

> > > > > the tracking is

> > > > > > working with a polar aligment compensation the only remaining issue

> > > > > is field rotation.

> > > > > > While field rortation is a big deal if you are using an alt-az mount

> > > > > without a wedge, once

> > > > > > you have gotten "pretty durn close" to polar aligned and have drift

> > > > > correction (like Gemini)

> > > > > > I don't think there'd be much need for a precise polar alignment

> > > > > except on real long

> > > > > > exposure work.

> > > > > >

> > > > > > maybe someone here can elaborate... .

> > > > > >

> > > > > > regards

> > > > > > Greg N

> > > > > >

> > > > > > --- In Losmandy_users@ yahoogroups. com, "Dave Kodama" kodama@>

> > > wrote:

> > > > > > >

> > > > > > > Rod,

> > > > > > >

> > > > > > > It's often a confusing issue, but the modeling (using lots of

> > > stars)

> > > > > > > is for go-to slewing accuracy and not tracking.

> > > > > > >

> > > > > > > If you want accurate tracking, you need to worry about polar

> > > > > > > alignment. How close it needs to be depends on your imaging

> > > > > > > requirements (how big your camera FOV is, how good your

> > > resolution,

> > > > > > > how long single exposures will be, etc.) I suggest aligning as

> > > well

> > > > > > > as you guess you need it to be, then do some test exposures and

> > > > see if

> > > > > > > you get field rotation in your shots. I think a lot of people

> > > sweat

> > > > > > > about really precise polar alignment without needing to.

> > > > > > >

> > > > > > > If you are guiding (i.e. using an autoguider or manually

> > > guiding the

> > > > > > > old way with an eyepiece), then the tracking rate you choose

> > > doesn't

> > > > > > > matter since the guiding will actively correct the mount's

> > > > tracking.

> > > > > > > So I just leave my mount set to sidereal tracking rate. The other

> > > > > > > tracking rates, including lunar and solar) are most useful in

> > > cases

> > > > > > > where you are *not* guiding like for visual use or say,

> > > > photographing

> > > > > > > a solar eclipse sequence.

> > > > > > >

> > > > > > > It's interesting that you found some odd interaction between the

> > > > King

> > > > > > > rate and the mount modeling, but I think that's not important.

> > > Just

> > > > > > > set it up using sidereal rate, then switch once you're done

> > > building

> > > > > > > the model. And as I said earlier, if you're guiding, just

> > > leave the

> > > > > > > mount in sidereal mode.

> > > > > > >

> > > > > > > Dave Kodama

> > > > > > >

> > > > > > >

> > > > > > > --- In Losmandy_users@ yahoogroups. com, Rod Mckay

> > > rodnscope@> wrote:

> > > > > > > >

> > > > > > > >

> > > > > > > > Hi,

> > > > > > > >

> > > > > > > > Couple of quesitons to the Guru's out there...

> > > > > > > >

> > > > > > > > 1. How close do people generally get their polar alignment in

> > > > > > > permanent installations? I'm in the process of setting up a

> > > > pier and

> > > > > > > can plonk the mount on and be within ~7' of the pole - is that

> > > > > > > reasonable, or should I spend more time trying to hone in closer?

> > > > > > > When adding more stars to the model it seems that the error jumps

> > > > > > > around by a few mninutes, so will I end up chasing my tail?

> > > > > > > >

> > > > > > > > I've previously tried using the Gemini polar alignment tools

> > > with

> > > > > > > varied success - it seems hit or miss whether you end up closer or

> > > > > not.

> > > > > > > >

> > > > > > > > 2. When auto guiding, do people generally have the mount set for

> > > > > > > Siderial or Adaptive King?

> > > > > > > >

> > > > > > > > 3. Is if odd that when using Siderial and doing a series of

> > > > > > > alignments I get a reported polar alignment error of ~ 7' on each

> > > > > > > axis, but when I do a number of alignments when set to Adaptive

> > > > King I

> > > > > > > get a reported polar alignment error of 30+' in each axis? I

> > > didn't

> > > > > > > touch the alt or az between alignments. Should I align on Siderial

> > > > > > > and then switch to Adaptive King?

> > > > > > > >

> > > > > > > > I'm sure I'll sort all this out in time, but I'd be

> > > interested to

> > > > > > > know if anyone has the answers.

> > > > > > > >

> > > > > > > > Cheers & thanks,

> > > > > > > > Rod

> > > > > > > >

> > > > > > > >

> > > > > > > > Make Yahoo!7 your homepage and win a trip to the Quiksilver

> > > > > > > Pro. Find out more

> > > > > > > >

> > > > > > >

> > > > > >

> > > > >

> > > >

> > > >

> > > >

> > > >

> > > >

> > > > Stay connected to the people that matter most with a smarter

> > > inbox. Take a look au.docs.yahoo.com/mail/smarterinbox

> > > >

> > > > [Non-text portions of this message have been removed]

> > > >

> > >

> >

>







----------------------------

#43852 Sep 3, 2009

you didn't say how you measure the amount of "tweak" you have applied in alt/az; are you using the gemini "Polar Axis Correction" function (under Align Telescope menu) described in section 3.4.2.3. of the gemini manual? (from the description of your visible sky, it sounds like polar align assist is not likely to be usable).



lee

--- In Losmandy_users@yahoogroups.com, Rod Mckay rodnscope@...> wrote:

>

> To date I've been relying on Gemini to tell me the polar alignment error, as it does after you've aligned the 3rd and subsequent stars.. I then tweak alt & az, cold reset the mount, and start again - to hopefully observer a smaller error.. My observing position is kind of limited, and drift alignment is a bit tricky from there......

>



----------------------------

#43854 Sep 3, 2009

I think you may still be unclear about what polar alignment does for you vs. Gemini modeling.



To clarify, polar alignment (adjustment of azimuth and altitude), sets the polar axis so that *tracking* is as accurate as possible when simply running the RA motor at the correct rate.



The Gemini modeling is used to accurately *slew* the scope to a selected coordinate. It will correct the slewing for errors in polar axis alignment, and also correct for mechanical problems such as flexing of the scope/mount in different parts of the sky. You do not have to be accurately polar aligned to do accurate slewing because the modeling corrects for this.



Thus a visual observer is generally concerned with accurate modeling and moderately concerned with accurate polar alignment. A wide field camera imager might be more concerned about accurate alignment and less with accurate modeling. But a CCD imager using a long focal length scope would be concerned with both. The accurate modeling would allow objects to be placed on the imaging chip, and accurate alignment would assure that it stayed there.



---------------



With that understanding, here's my recommendation of a setup sequence, assuming you have a portable setup.



- Rough align the mount using compass and level and set the

altitude adjustment to your latitude.



- Using the polar alignment scope, refine the altitude and

azimuth adjustment.



- Place the mount in the counterweight-down (CWD) position.

I just do this by eyeball. Extreme accuracy is not

necessary.



- Turn on the mount and insure that it cold-starts with the

correct time and other parameters.



- Align Gemini to as few as one star.



- Use the Gemini polar alignment routines and/or drift

align to refine the altitude and azimuth adjustmnent.

This is the step at which you need to sweat getting

as close as possible to exact alignment, depending

on your tracking requirements.



- Go back to the CWD position and cold-start. From this

point on, do not release the clutches.



- Proceed with Gemini alignment modeling. When you select

the first star, the slew might be off, but just use your

finder to get close and then use your scope and high mag

eyepiece to center it. Subsequent alignment stars will

probably be in the scope eyepiece. Use as many stars

as you need to in order to get slewing as accurate

as desired for your requirements.



---------------



Other procedures might be used to make things go faster/easier with the help of a computer and software, but the above is my suggestion for a basic approach. Experience is the only way to know just how much time you need to spend adjusting things to get the accuracy you need...



Hope that was helpful!



Dave



--- In Losmandy_users@yahoogroups.com, "ott_je" jc.ott@...> wrote:

>

>

> Thanks for the reply Dave and others,

>

> I'm fairly well versed in the mount setup with leveling, using the Polar Alignment Scope, Counter Weight Down (except that I've had issues with getting the CWD really set accurately so if anyone has any tips on this one I'd welcome them), startup, doing a syncronize, additional aligns, and the Polar Axis Correction function.

>

> So, I'm still a bit confused about where I go from there and how I should proceed to do an accurate two star drift alignment. I'm still not clear on whether the modeling or the drift alignment comes first???

>

> You mention that I should not release the clutches so should I goto particular alignment stars to get started with the drift align??

>

> And, after the drift align is done, will the mount do accurate goto's? In other words, is the modeling preserved?

>

> Thanks and sorry for the confusion. I've seen and read so many examples on the Internet that my head is spinning. I appreciate yours and anyone else's help with this matter.

>

> Best regards,

> Jerry.

>

>

>

>

>

>

> --- In Losmandy_users@yahoogroups.com, "d_kodama" kodama@> wrote:

> >

> > Jerry,

> >

> > I do drift alignment first. Or you can use the iterative Gemini procedures to align.

> >

> > Either way, for accurate tracking for long exposures, you want to set your mount's altitude and azimuth adjustment accurately *first*. Then do your modeling, which is used for go-to slews.

> >

> > When doing your modeling for the first time, you first want to power up in the counterweight-down position with a cold-start. This is so the Gemini knows where the mount is positioned physically to start. It's important to start up properly so the slews don't cause the mount to go past the safety limits. After this is done, you never should release the clutches.

> >

> > The modeling is done by letting the Gemini slew to the selected alignment stars. Assuming you have set the correct time and other mount parameters, it should slew fairly close to the first alignment star you select, then you use the paddle to tweak the position in your scope (i.e. not by releasing the clutches). Subsequent alignment stars are handled the same way and you should find the Gemini slews getting closer and closer to being right on target.

> >

> > If I'm just going to be doing long exposures and not requiring a lot of accurate slewing (e.g. for a night of widefield shots), after polar axis alignment, I just use one star or just a small handful for the model (after clearing out any old model remaining in memory).

> >

> > Dave

> >

> >

> > --- In Losmandy_users@yahoogroups.com, "ott_je" jc.ott@> wrote:

> > >

> > >

> > > Dave,

> > >

> > > I pretty new to using my new GM-8 with Gemini. I see from your post below that you use drift alignment for Astrophotography. I've been attempting to find out the procedures, step-by-step, that are necessaary to drift align my system.

> > >

> > > Questions I have are whether or not to do modeling, etc prior to drift alignment?? Do you slew the scope to alignment stars or can one simply use the clutches to get the scope close and then slew to get the star centered??

> > >

> > > Anyway, I really need some help with this deal as I'm interested in fairly long exposure periods without error.

> > >

> > > Thanks,

> > > Jerry.

> > >

> > >

> > > --- In Losmandy_users@yahoogroups.com, "Dave Kodama" kodama@> wrote:

> > > >

> > > > Rod,

> > > >

> > > > Sounds like you're on the right path. Since you're using autoguiding,

> > > > there's no reason to mess with Adaptive King or anything but sidereal

> > > > rate.

> > > >

> > > > The only thing I might suggest is to use the Gemini polar axis

> > > > correction routine rather than just depend on the error numbers

> > > > resulting from running the modeling procedure (I haven't used it

> > > > seriously myself except to try it as I use drift alignment normally).

> > > >

> > > > Dave

> > > >

> > > >

> > > >

> > > > --- In Losmandy_users@yahoogroups.com, Rod Mckay rodnscope@> wrote:

> > > > >

> > > > > Thanks Guys.

> > > > >

> > > > > I do see a little bit of field rotation, but it generally manifests

> > > > as 0.01 degrees per 2 or 3 10 minute exposures, so isn't too bad.. The

> > > > equipment I'm imaging with is a WO FLT110 refractor and modified Canon

> > > > 350D DSLR, guided through a WO ZS66SD with Imaging Source DMK21 USB

> > > > camera via GuideMaster software.. I have more of an issue with

> > > > differential flexure, which I've managed to substantially reduce, and

> > > > suspect the remaining 1-2 pixel drift per 10 min expsoure may be the

> > > > FLT110 focuser sagging slightly, as I'm running out of other options.

> > > > >

> > > > > To date I've been relying on Gemini to tell me the polar alignment

> > > > error, as it does after you've aligned the 3rd and subsequent stars..

> > > > I then tweak alt & az, cold reset the mount, and start again - to

> > > > hopefully observer a smaller error.. My observing position is kind of

> > > > limited, and drift alignment is a bit tricky from there. - my view

> > > > East is blocked by our house, and my wife's 2+m Jeruslem Artichokes

> > > > currently obscure the view to the West, so my view is largely "Up",

> > > > which is fine for imaging as I can usually get 3+hrs of imaging in for

> > > > most objects if I catch them when they're just prior to straight up

> > > > (ie. mount just rotated past the verticle).. Visually I'm as "on the

> > > > pole" as I could be when I look through the scope, but that makes no

> > > > allowance for less than perfect mounting which is bound to be the case.

> > > > >

> > > > > While I've got a pier, it's the only bit that's permanent - the rest

> > > > of my kit comes in every night.. It was my hope that once I got

> > > > alignment good, and assuming alt and az is well locked down, I should

> > > > be able to get repeatably close enough by just taking the mount out

> > > > and plonking it down on the MA adapter.. This seems to be the case,

> > > > but is one reason I have yet to get fussy about perfect alignment.

> > > > >

> > > > > So, the plan looks like it should be to continue to chip away at

> > > > better alignment but to not get too worried about being perfect.. Also

> > > > not to worry about using Adaptive King.

> > > > >

> > > > > Cheers & thanks,

> > > > > Rod

> > > > >

> > > > >

> > > > >

> > > > >

> > > > >

---------------

> > > > > From: Dave Kodama kodama@>

> > > > > To: Losmandy_users@yahoogroups.com

> > > > > Sent: Friday, 20 February, 2009 8:09:14 PM

> > > > > Subject: [Losmandy_users] Re: Polar Alignment / Guiding Tracking

> > > > >

> > > > >

> > > > > Greg,

> > > > >

> > > > > Sorry, I should have checked the manual first. I think you're

> > > > > referring to "closed loop" tracking. This is OK for visual use but

> > > > > being misaligned will still result in field rotation. Also, tracking

> > > > > in the DEC axis will start to cause PE errors from that axis to

> > > > > complicate the tracking errors.

> > > > >

> > > > > Anyway, going back to the question of how good your polar alignment

> > > > > has to be... how much rotation you can tolerate in a photo depends on

> > > > > all the factors I mentioned earlier, so it's really not possible to

> > > > > give one number which is good enough for all imaging setups. Shooting

> > > > > 4x5 film photos requires much, much more accurate alignment than

> > > > > 2-minute sub-exposures with an APS-sized DSLR sensor.

> > > > >

> > > > > Dave

> > > > >

> > > > > --- In Losmandy_users@ yahoogroups. com, "Dave Kodama" kodama@> wrote:

> > > > > >

> > > > > > Greg,

> > > > > >

> > > > > > Aside from tweaking the tracking rate constants or periodic error

> > > > > > correction which are RA-axis-only adjustments, I was not aware of any

> > > > > > kind of tracking compensation that is done based on computed polar

> > > > > > misalignment. For this to work, the mount would have to move in both

> > > > > > RA and DEC. Can you explain the tracking error compensation you're

> > > > > > referring to?

> > > > > >

> > > > > > Dave

> > > > > >

> > > > > >

> > > > > > --- In Losmandy_users@ yahoogroups. com, "gnowellsct" tim71pos@>

> > > > wrote:

> > > > > > >

> > > > > > > Actually Gemini has a tracking error compensation so the below is

> > > > > > not strictly speaking

> > > > > > > true. For shorter exposures, I'd guess five to ten minutes, a

> > > > > > "kinda oK aligned scope" say

> > > > > > > to within 15 arc minutes of the pole may not show that much field

> > > > > > rotation to merit

> > > > > > > zeroing in on the polar alignment.

> > > > > > >

> > > > > > > Wiser heads than me may have some views on that. But basically once

> > > > > > the tracking is

> > > > > > > working with a polar aligment compensation the only remaining issue

> > > > > > is field rotation.

> > > > > > > While field rortation is a big deal if you are using an alt-az mount

> > > > > > without a wedge, once

> > > > > > > you have gotten "pretty durn close" to polar aligned and have drift

> > > > > > correction (like Gemini)

> > > > > > > I don't think there'd be much need for a precise polar alignment

> > > > > > except on real long

> > > > > > > exposure work.

> > > > > > >

> > > > > > > maybe someone here can elaborate... .

> > > > > > >

> > > > > > > regards

> > > > > > > Greg N

> > > > > > >

> > > > > > > --- In Losmandy_users@ yahoogroups. com, "Dave Kodama" kodama@>

> > > > wrote:

> > > > > > > >

> > > > > > > > Rod,

> > > > > > > >

> > > > > > > > It's often a confusing issue, but the modeling (using lots of

> > > > stars)

> > > > > > > > is for go-to slewing accuracy and not tracking.

> > > > > > > >

> > > > > > > > If you want accurate tracking, you need to worry about polar

> > > > > > > > alignment. How close it needs to be depends on your imaging

> > > > > > > > requirements (how big your camera FOV is, how good your

> > > > resolution,

> > > > > > > > how long single exposures will be, etc.) I suggest aligning as

> > > > well

> > > > > > > > as you guess you need it to be, then do some test exposures and

> > > > > see if

> > > > > > > > you get field rotation in your shots. I think a lot of people

> > > > sweat

> > > > > > > > about really precise polar alignment without needing to.

> > > > > > > >

> > > > > > > > If you are guiding (i.e. using an autoguider or manually

> > > > guiding the

> > > > > > > > old way with an eyepiece), then the tracking rate you choose

> > > > doesn't

> > > > > > > > matter since the guiding will actively correct the mount's

> > > > > tracking.

> > > > > > > > So I just leave my mount set to sidereal tracking rate. The other

> > > > > > > > tracking rates, including lunar and solar) are most useful in

> > > > cases

> > > > > > > > where you are *not* guiding like for visual use or say,

> > > > > photographing

> > > > > > > > a solar eclipse sequence.

> > > > > > > >

> > > > > > > > It's interesting that you found some odd interaction between the

> > > > > King

> > > > > > > > rate and the mount modeling, but I think that's not important.

> > > > Just

> > > > > > > > set it up using sidereal rate, then switch once you're done

> > > > building

> > > > > > > > the model. And as I said earlier, if you're guiding, just

> > > > leave the

> > > > > > > > mount in sidereal mode.

> > > > > > > >

> > > > > > > > Dave Kodama

> > > > > > > >

> > > > > > > >

> > > > > > > > --- In Losmandy_users@ yahoogroups. com, Rod Mckay

> > > > rodnscope@> wrote:

> > > > > > > > >

> > > > > > > > >

> > > > > > > > > Hi,

> > > > > > > > >

> > > > > > > > > Couple of quesitons to the Guru's out there...

> > > > > > > > >

> > > > > > > > > 1. How close do people generally get their polar alignment in

> > > > > > > > permanent installations? I'm in the process of setting up a

> > > > > pier and

> > > > > > > > can plonk the mount on and be within ~7' of the pole - is that

> > > > > > > > reasonable, or should I spend more time trying to hone in closer?

> > > > > > > > When adding more stars to the model it seems that the error jumps

> > > > > > > > around by a few mninutes, so will I end up chasing my tail?

> > > > > > > > >

> > > > > > > > > I've previously tried using the Gemini polar alignment tools

> > > > with

> > > > > > > > varied success - it seems hit or miss whether you end up closer or

> > > > > > not.

> > > > > > > > >

> > > > > > > > > 2. When auto guiding, do people generally have the mount set for

> > > > > > > > Siderial or Adaptive King?

> > > > > > > > >

> > > > > > > > > 3. Is if odd that when using Siderial and doing a series of

> > > > > > > > alignments I get a reported polar alignment error of ~ 7' on each

> > > > > > > > axis, but when I do a number of alignments when set to Adaptive

> > > > > King I

> > > > > > > > get a reported polar alignment error of 30+' in each axis? I

> > > > didn't

> > > > > > > > touch the alt or az between alignments. Should I align on Siderial

> > > > > > > > and then switch to Adaptive King?

> > > > > > > > >

> > > > > > > > > I'm sure I'll sort all this out in time, but I'd be

> > > > interested to

> > > > > > > > know if anyone has the answers.

> > > > > > > > >

> > > > > > > > > Cheers & thanks,

> > > > > > > > > Rod

> > > > > > > > >

> > > > > > > > >

> > > > > > > > > Make Yahoo!7 your homepage and win a trip to the Quiksilver

> > > > > > > > Pro. Find out more

> > > > > > > > >

> > > > > > > >

> > > > > > >

> > > > > >

> > > > >

> > > > >

> > > > >

> > > > >

> > > > >

> > > > > Stay connected to the people that matter most with a smarter

> > > > inbox. Take a look au.docs.yahoo.com/mail/smarterinbox

> > > > >

> > > > > [Non-text portions of this message have been removed]

> > > > >

> > > >

> > >

> >

>







----------------------------

#43861 Sep 3, 2009

Thanks Dave for all the information,



You made this statement:



- "Use the Gemini polar alignment routines and/or drift

align to refine the altitude and azimuth adjustment.

This is the step at which you need to sweat getting

as close as possible to exact alignment, depending

on your tracking requirements."



I apologize that I must not have made myself very clear. Since I want to do long exposure photography, I need to know HOW to drift align my system and have the ability to make accurate goto's. It seems that you must have assumed that I know how to do a drift alignment from what I've told you. That, my friend, couldn't be farther from the truth. :-) I'm merely wanting to know how to do the two star drift alignment procedure with this system and where it fits in with the modeling routine.



So...from what I understand, you do the leveling, initial Polar Alignment, then align on one star and then from there do the drift alignment. After that, do a "Park Mount" function, cold start, and then go through the full up synchronize and additional align functions to make sure the goto's are on target. Is this correct?



So...bottom line, what I really need is the procedures you use to do a proper drift alignment and setup the mount for accurate goto's.



Thanks,

Jerry.



--- In Losmandy_users@yahoogroups.com, "d_kodama" kodama@...> wrote:

>

> I think you may still be unclear about what polar alignment does for you vs. Gemini modeling.

>

> To clarify, polar alignment (adjustment of azimuth and altitude), sets the polar axis so that *tracking* is as accurate as possible when simply running the RA motor at the correct rate.

>

> The Gemini modeling is used to accurately *slew* the scope to a selected coordinate. It will correct the slewing for errors in polar axis alignment, and also correct for mechanical problems such as flexing of the scope/mount in different parts of the sky. You do not have to be accurately polar aligned to do accurate slewing because the modeling corrects for this.

>

> Thus a visual observer is generally concerned with accurate modeling and moderately concerned with accurate polar alignment. A wide field camera imager might be more concerned about accurate alignment and less with accurate modeling. But a CCD imager using a long focal length scope would be concerned with both. The accurate modeling would allow objects to be placed on the imaging chip, and accurate alignment would assure that it stayed there.

>

---------------

>

> With that understanding, here's my recommendation of a setup sequence, assuming you have a portable setup.

>

> - Rough align the mount using compass and level and set the

> altitude adjustment to your latitude.

>

> - Using the polar alignment scope, refine the altitude and

> azimuth adjustment.

>

> - Place the mount in the counterweight-down (CWD) position.

> I just do this by eyeball. Extreme accuracy is not

> necessary.

>

> - Turn on the mount and insure that it cold-starts with the

> correct time and other parameters.

>

> - Align Gemini to as few as one star.

>

> - Use the Gemini polar alignment routines and/or drift

> align to refine the altitude and azimuth adjustmnent.

> This is the step at which you need to sweat getting

> as close as possible to exact alignment, depending

> on your tracking requirements.

>

> - Go back to the CWD position and cold-start. From this

> point on, do not release the clutches.

>

> - Proceed with Gemini alignment modeling. When you select

> the first star, the slew might be off, but just use your

> finder to get close and then use your scope and high mag

> eyepiece to center it. Subsequent alignment stars will

> probably be in the scope eyepiece. Use as many stars

> as you need to in order to get slewing as accurate

> as desired for your requirements.

>

---------------

>

> Other procedures might be used to make things go faster/easier with the help of a computer and software, but the above is my suggestion for a basic approach. Experience is the only way to know just how much time you need to spend adjusting things to get the accuracy you need...

>

> Hope that was helpful!

>

> Dave

>

>

> --- In Losmandy_users@yahoogroups.com, "ott_je" jc.ott@> wrote:

> >

> >

> > Thanks for the reply Dave and others,

> >

> > I'm fairly well versed in the mount setup with leveling, using the Polar Alignment Scope, Counter Weight Down (except that I've had issues with getting the CWD really set accurately so if anyone has any tips on this one I'd welcome them), startup, doing a syncronize, additional aligns, and the Polar Axis Correction function.

> >

> > So, I'm still a bit confused about where I go from there and how I should proceed to do an accurate two star drift alignment. I'm still not clear on whether the modeling or the drift alignment comes first???

> >

> > You mention that I should not release the clutches so should I goto particular alignment stars to get started with the drift align??

> >

> > And, after the drift align is done, will the mount do accurate goto's? In other words, is the modeling preserved?

> >

> > Thanks and sorry for the confusion. I've seen and read so many examples on the Internet that my head is spinning. I appreciate yours and anyone else's help with this matter.

> >

> > Best regards,

> > Jerry.

> >

> >

> >

> >

> >

> >

> > --- In Losmandy_users@yahoogroups.com, "d_kodama" kodama@> wrote:

> > >

> > > Jerry,

> > >

> > > I do drift alignment first. Or you can use the iterative Gemini procedures to align.

> > >

> > > Either way, for accurate tracking for long exposures, you want to set your mount's altitude and azimuth adjustment accurately *first*. Then do your modeling, which is used for go-to slews.

> > >

> > > When doing your modeling for the first time, you first want to power up in the counterweight-down position with a cold-start. This is so the Gemini knows where the mount is positioned physically to start. It's important to start up properly so the slews don't cause the mount to go past the safety limits. After this is done, you never should release the clutches.

> > >

> > > The modeling is done by letting the Gemini slew to the selected alignment stars. Assuming you have set the correct time and other mount parameters, it should slew fairly close to the first alignment star you select, then you use the paddle to tweak the position in your scope (i.e. not by releasing the clutches). Subsequent alignment stars are handled the same way and you should find the Gemini slews getting closer and closer to being right on target.

> > >

> > > If I'm just going to be doing long exposures and not requiring a lot of accurate slewing (e.g. for a night of widefield shots), after polar axis alignment, I just use one star or just a small handful for the model (after clearing out any old model remaining in memory).

> > >

> > > Dave

> > >

> > >

> > > --- In Losmandy_users@yahoogroups.com, "ott_je" jc.ott@> wrote:

> > > >

> > > >

> > > > Dave,

> > > >

> > > > I pretty new to using my new GM-8 with Gemini. I see from your post below that you use drift alignment for Astrophotography. I've been attempting to find out the procedures, step-by-step, that are necessaary to drift align my system.

> > > >

> > > > Questions I have are whether or not to do modeling, etc prior to drift alignment?? Do you slew the scope to alignment stars or can one simply use the clutches to get the scope close and then slew to get the star centered??

> > > >

> > > > Anyway, I really need some help with this deal as I'm interested in fairly long exposure periods without error.

> > > >

> > > > Thanks,

> > > > Jerry.

> > > >

> > > >

> > > > --- In Losmandy_users@yahoogroups.com, "Dave Kodama" kodama@> wrote:

> > > > >

> > > > > Rod,

> > > > >

> > > > > Sounds like you're on the right path. Since you're using autoguiding,

> > > > > there's no reason to mess with Adaptive King or anything but sidereal

> > > > > rate.

> > > > >

> > > > > The only thing I might suggest is to use the Gemini polar axis

> > > > > correction routine rather than just depend on the error numbers

> > > > > resulting from running the modeling procedure (I haven't used it

> > > > > seriously myself except to try it as I use drift alignment normally).

> > > > >

> > > > > Dave

> > > > >

> > > > >

> > > > >

> > > > > --- In Losmandy_users@yahoogroups.com, Rod Mckay rodnscope@> wrote:

> > > > > >

> > > > > > Thanks Guys.

> > > > > >

> > > > > > I do see a little bit of field rotation, but it generally manifests

> > > > > as 0.01 degrees per 2 or 3 10 minute exposures, so isn't too bad.. The

> > > > > equipment I'm imaging with is a WO FLT110 refractor and modified Canon

> > > > > 350D DSLR, guided through a WO ZS66SD with Imaging Source DMK21 USB

> > > > > camera via GuideMaster software.. I have more of an issue with

> > > > > differential flexure, which I've managed to substantially reduce, and

> > > > > suspect the remaining 1-2 pixel drift per 10 min expsoure may be the

> > > > > FLT110 focuser sagging slightly, as I'm running out of other options.

> > > > > >

> > > > > > To date I've been relying on Gemini to tell me the polar alignment

> > > > > error, as it does after you've aligned the 3rd and subsequent stars..

> > > > > I then tweak alt & az, cold reset the mount, and start again - to

> > > > > hopefully observer a smaller error.. My observing position is kind of

> > > > > limited, and drift alignment is a bit tricky from there. - my view

> > > > > East is blocked by our house, and my wife's 2+m Jeruslem Artichokes

> > > > > currently obscure the view to the West, so my view is largely "Up",

> > > > > which is fine for imaging as I can usually get 3+hrs of imaging in for

> > > > > most objects if I catch them when they're just prior to straight up

> > > > > (ie. mount just rotated past the verticle).. Visually I'm as "on the

> > > > > pole" as I could be when I look through the scope, but that makes no

> > > > > allowance for less than perfect mounting which is bound to be the case.

> > > > > >

> > > > > > While I've got a pier, it's the only bit that's permanent - the rest

> > > > > of my kit comes in every night.. It was my hope that once I got

> > > > > alignment good, and assuming alt and az is well locked down, I should

> > > > > be able to get repeatably close enough by just taking the mount out

> > > > > and plonking it down on the MA adapter.. This seems to be the case,

> > > > > but is one reason I have yet to get fussy about perfect alignment.

> > > > > >

> > > > > > So, the plan looks like it should be to continue to chip away at

> > > > > better alignment but to not get too worried about being perfect.. Also

> > > > > not to worry about using Adaptive King.

> > > > > >

> > > > > > Cheers & thanks,

> > > > > > Rod

> > > > > >

> > > > > >

> > > > > >

> > > > > >

> > > > > >

---------------

> > > > > > From: Dave Kodama kodama@>

> > > > > > To: Losmandy_users@yahoogroups.com

> > > > > > Sent: Friday, 20 February, 2009 8:09:14 PM

> > > > > > Subject: [Losmandy_users] Re: Polar Alignment / Guiding Tracking

> > > > > >

> > > > > >

> > > > > > Greg,

> > > > > >

> > > > > > Sorry, I should have checked the manual first. I think you're

> > > > > > referring to "closed loop" tracking. This is OK for visual use but

> > > > > > being misaligned will still result in field rotation. Also, tracking

> > > > > > in the DEC axis will start to cause PE errors from that axis to

> > > > > > complicate the tracking errors.

> > > > > >

> > > > > > Anyway, going back to the question of how good your polar alignment

> > > > > > has to be... how much rotation you can tolerate in a photo depends on

> > > > > > all the factors I mentioned earlier, so it's really not possible to

> > > > > > give one number which is good enough for all imaging setups. Shooting

> > > > > > 4x5 film photos requires much, much more accurate alignment than

> > > > > > 2-minute sub-exposures with an APS-sized DSLR sensor.

> > > > > >

> > > > > > Dave

> > > > > >

> > > > > > --- In Losmandy_users@ yahoogroups. com, "Dave Kodama" kodama@> wrote:

> > > > > > >

> > > > > > > Greg,

> > > > > > >

> > > > > > > Aside from tweaking the tracking rate constants or periodic error

> > > > > > > correction which are RA-axis-only adjustments, I was not aware of any

> > > > > > > kind of tracking compensation that is done based on computed polar

> > > > > > > misalignment. For this to work, the mount would have to move in both

> > > > > > > RA and DEC. Can you explain the tracking error compensation you're

> > > > > > > referring to?

> > > > > > >

> > > > > > > Dave

> > > > > > >

> > > > > > >

> > > > > > > --- In Losmandy_users@ yahoogroups. com, "gnowellsct" tim71pos@>

> > > > > wrote:

> > > > > > > >

> > > > > > > > Actually Gemini has a tracking error compensation so the below is

> > > > > > > not strictly speaking

> > > > > > > > true. For shorter exposures, I'd guess five to ten minutes, a

> > > > > > > "kinda oK aligned scope" say

> > > > > > > > to within 15 arc minutes of the pole may not show that much field

> > > > > > > rotation to merit

> > > > > > > > zeroing in on the polar alignment.

> > > > > > > >

> > > > > > > > Wiser heads than me may have some views on that. But basically once

> > > > > > > the tracking is

> > > > > > > > working with a polar aligment compensation the only remaining issue

> > > > > > > is field rotation.

> > > > > > > > While field rortation is a big deal if you are using an alt-az mount

> > > > > > > without a wedge, once

> > > > > > > > you have gotten "pretty durn close" to polar aligned and have drift

> > > > > > > correction (like Gemini)

> > > > > > > > I don't think there'd be much need for a precise polar alignment

> > > > > > > except on real long

> > > > > > > > exposure work.

> > > > > > > >

> > > > > > > > maybe someone here can elaborate... .

> > > > > > > >

> > > > > > > > regards

> > > > > > > > Greg N

> > > > > > > >

> > > > > > > > --- In Losmandy_users@ yahoogroups. com, "Dave Kodama" kodama@>

> > > > > wrote:

> > > > > > > > >

> > > > > > > > > Rod,

> > > > > > > > >

> > > > > > > > > It's often a confusing issue, but the modeling (using lots of

> > > > > stars)

> > > > > > > > > is for go-to slewing accuracy and not tracking.

> > > > > > > > >

> > > > > > > > > If you want accurate tracking, you need to worry about polar

> > > > > > > > > alignment. How close it needs to be depends on your imaging

> > > > > > > > > requirements (how big your camera FOV is, how good your

> > > > > resolution,

> > > > > > > > > how long single exposures will be, etc.) I suggest aligning as

> > > > > well

> > > > > > > > > as you guess you need it to be, then do some test exposures and

> > > > > > see if

> > > > > > > > > you get field rotation in your shots. I think a lot of people

> > > > > sweat

> > > > > > > > > about really precise polar alignment without needing to.

> > > > > > > > >

> > > > > > > > > If you are guiding (i.e. using an autoguider or manually

> > > > > guiding the

> > > > > > > > > old way with an eyepiece), then the tracking rate you choose

> > > > > doesn't

> > > > > > > > > matter since the guiding will actively correct the mount's

> > > > > > tracking.

> > > > > > > > > So I just leave my mount set to sidereal tracking rate. The other

> > > > > > > > > tracking rates, including lunar and solar) are most useful in

> > > > > cases

> > > > > > > > > where you are *not* guiding like for visual use or say,

> > > > > > photographing

> > > > > > > > > a solar eclipse sequence.

> > > > > > > > >

> > > > > > > > > It's interesting that you found some odd interaction between the

> > > > > > King

> > > > > > > > > rate and the mount modeling, but I think that's not important.

> > > > > Just

> > > > > > > > > set it up using sidereal rate, then switch once you're done

> > > > > building

> > > > > > > > > the model. And as I said earlier, if you're guiding, just

> > > > > leave the

> > > > > > > > > mount in sidereal mode.

> > > > > > > > >

> > > > > > > > > Dave Kodama

> > > > > > > > >

> > > > > > > > >

> > > > > > > > > --- In Losmandy_users@ yahoogroups. com, Rod Mckay

> > > > > rodnscope@> wrote:

> > > > > > > > > >

> > > > > > > > > >

> > > > > > > > > > Hi,

> > > > > > > > > >

> > > > > > > > > > Couple of quesitons to the Guru's out there...

> > > > > > > > > >

> > > > > > > > > > 1. How close do people generally get their polar alignment in

> > > > > > > > > permanent installations? I'm in the process of setting up a

> > > > > > pier and

> > > > > > > > > can plonk the mount on and be within ~7' of the pole - is that

> > > > > > > > > reasonable, or should I spend more time trying to hone in closer?

> > > > > > > > > When adding more stars to the model it seems that the error jumps

> > > > > > > > > around by a few mninutes, so will I end up chasing my tail?

> > > > > > > > > >

> > > > > > > > > > I've previously tried using the Gemini polar alignment tools

> > > > > with

> > > > > > > > > varied success - it seems hit or miss whether you end up closer or

> > > > > > > not.

> > > > > > > > > >

> > > > > > > > > > 2. When auto guiding, do people generally have the mount set for

> > > > > > > > > Siderial or Adaptive King?

> > > > > > > > > >

> > > > > > > > > > 3. Is if odd that when using Siderial and doing a series of

> > > > > > > > > alignments I get a reported polar alignment error of ~ 7' on each

> > > > > > > > > axis, but when I do a number of alignments when set to Adaptive

> > > > > > King I

> > > > > > > > > get a reported polar alignment error of 30+' in each axis? I

> > > > > didn't

> > > > > > > > > touch the alt or az between alignments. Should I align on Siderial

> > > > > > > > > and then switch to Adaptive King?

> > > > > > > > > >

> > > > > > > > > > I'm sure I'll sort all this out in time, but I'd be

> > > > > interested to

> > > > > > > > > know if anyone has the answers.

> > > > > > > > > >

> > > > > > > > > > Cheers & thanks,

> > > > > > > > > > Rod

> > > > > > > > > >

> > > > > > > > > >

> > > > > > > > > > Make Yahoo!7 your homepage and win a trip to the Quiksilver

> > > > > > > > > Pro. Find out more

> > > > > > > > > >

> > > > > > > > >

> > > > > > > >

> > > > > > >

> > > > > >

> > > > > >

> > > > > >

> > > > > >

> > > > > >

> > > > > > Stay connected to the people that matter most with a smarter

> > > > > inbox. Take a look au.docs.yahoo.com/mail/smarterinbox

> > > > > >

> > > > > > [Non-text portions of this message have been removed]

> > > > > >

> > > > >

> > > >

> > >

> >

>







----------------------------

#43864 Sep 3, 2009

here is what i do...



1. rough polar align -- which means, level the mount, rough visual alignment of the RA axis in North-South direction (stand on the south side of the mount and "point" it north), altitude adjustment of the RA axis equal to your latitude. takes 2 minutes. if you can not see polaris, it helps to keep a compass and angle level with your gear if go to a new place. also need to know your approximate magnetic declination adjustment to correct magnetic north for true north (easy to find on the web). if you are in the same place most of the time, you only need to do the rough altitude adjustment once and eyeball true north.



2. use your polar axis scope to refine polar alignment (assuming you have one). takes a few minutes (once you get the hang of it) and i find this is usually within 20-30min accuracy in alt and azi. if you don't have a PAS, just naked-eye sight align through the RA axis shaft so you can see polaris (you will have to rotate the scope in DEC to align the dec axis opening with the RA shaft interior). these alignment adjustments involve alt and az adjustments to the mount head. not moving the scope in RA and DEC.



3. turn on the scope. dont worry about start-up, sync, etc. just put it in sidereal tracking mode (you are not going to slew to anything yet so it does not matter that the scope does not know where it is pointing)



4. now drift align -- search the web and you will find plenty of explanations. use a higher power eyepiece with illuminated cross hair reticle (and barlow). manually move the scope to pick your star for polar alignment -- one to the south and one to the east (ideally). here is a good explanation of the adjustments. like i said, search the web and you can find plenty more if this one is not clear.



www.astropix.com/HTML/I_ASTROP/TRACKED/POLAR.HTM



this usually takes me 30-40 minutes. some consider that long, i consider it peaceful.



OK, after you do all that (if you want/need to because you plan on taking pictures), then put the mount in CWD position and cold start to begin the synchronization and model building. after doing some model building, you can use the gemini polar axis correction function for some improvement. the best alignment i have ever achieved was 1min in az and elev. most of the time it is 5-8min. by the time i do all that, an hour has gone by (and i am relaxed :-)



if you only want visual tracking, you can probably get away with only the first step (and second without PAS). if you have a polar axis scope, throw that in too for good measure and you can probably track for an hour without losing an image from view.



you can start even before total darkness. some bright stars are visible shortly after sundown.



>

> Thanks Dave for all the information,

>

> You made this statement:

>

> - "Use the Gemini polar alignment routines and/or drift

> align to refine the altitude and azimuth adjustment.

> This is the step at which you need to sweat getting

> as close as possible to exact alignment, depending

> on your tracking requirements."

>

> I apologize that I must not have made myself very clear. Since I want to do long exposure photography, I need to know HOW to drift align my system and have the ability to make accurate goto's. It seems that you must have assumed that I know how to do a drift alignment from what I've told you. That, my friend, couldn't be farther from the truth. :-) I'm merely wanting to know how to do the two star drift alignment procedure with this system and where it fits in with the modeling routine.

>



----------------------------

#43866 Sep 4, 2009

Thanks for the reply, I appreciate it.



You said to "manually" move the mount to the stars for drift alignment. Do you actually mean to release the clutches or do you mean to manually slew to each of the two stars?



Another question comes to mind. May a person turn off the Gemini to determine direction in the eyepiece or does that totally throw all adjustments out the window? Just interested to know what is done to achieve knowledge of East, West, North, South in the eyepiece.



Thanks,

Jerry.









-- In Losmandy_users@yahoogroups.com, "lmbuck2000" lmbuck2000@...> wrote: >

> here is what i do...

>

> 1. rough polar align -- which means, level the mount, rough visual alignment of the RA axis in North-South direction (stand on the south side of the mount and "point" it north), altitude adjustment of the RA axis equal to your latitude. takes 2 minutes. if you can not see polaris, it helps to keep a compass and angle level with your gear if go to a new place. also need to know your approximate magnetic declination adjustment to correct magnetic north for true north (easy to find on the web). if you are in the same place most of the time, you only need to do the rough altitude adjustment once and eyeball true north.

>

> 2. use your polar axis scope to refine polar alignment (assuming you have one). takes a few minutes (once you get the hang of it) and i find this is usually within 20-30min accuracy in alt and azi. if you don't have a PAS, just naked-eye sight align through the RA axis shaft so you can see polaris (you will have to rotate the scope in DEC to align the dec axis opening with the RA shaft interior). these alignment adjustments involve alt and az adjustments to the mount head. not moving the scope in RA and DEC.

>

> 3. turn on the scope. dont worry about start-up, sync, etc. just put it in sidereal tracking mode (you are not going to slew to anything yet so it does not matter that the scope does not know where it is pointing)

>

> 4. now drift align -- search the web and you will find plenty of explanations. use a higher power eyepiece with illuminated cross hair reticle (and barlow). manually move the scope to pick your star for polar alignment -- one to the south and one to the east (ideally). here is a good explanation of the adjustments. like i said, search the web and you can find plenty more if this one is not clear.

>

> www.astropix.com/HTML/I_ASTROP/TRACKED/POLAR.HTM

>

> this usually takes me 30-40 minutes. some consider that long, i consider it peaceful.

>

> OK, after you do all that (if you want/need to because you plan on taking pictures), then put the mount in CWD position and cold start to begin the synchronization and model building. after doing some model building, you can use the gemini polar axis correction function for some improvement. the best alignment i have ever achieved was 1min in az and elev. most of the time it is 5-8min. by the time i do all that, an hour has gone by (and i am relaxed :-)

>

> if you only want visual tracking, you can probably get away with only the first step (and second without PAS). if you have a polar axis scope, throw that in too for good measure and you can probably track for an hour without losing an image from view.

>

> you can start even before total darkness. some bright stars are visible shortly after sundown.

>

>

> >

> > Thanks Dave for all the information,

> >

> > You made this statement:

> >

> > - "Use the Gemini polar alignment routines and/or drift

> > align to refine the altitude and azimuth adjustment.

> > This is the step at which you need to sweat getting

> > as close as possible to exact alignment, depending

> > on your tracking requirements."

> >

> > I apologize that I must not have made myself very clear. Since I want to do long exposure photography, I need to know HOW to drift align my system and have the ability to make accurate goto's. It seems that you must have assumed that I know how to do a drift alignment from what I've told you. That, my friend, couldn't be farther from the truth. :-) I'm merely wanting to know how to do the two star drift alignment procedure with this system and where it fits in with the modeling routine.

> >

>







----------------------------

#43869 Sep 4, 2009

you can release the clutches and manually move the scope OR use slewing... just dont try to "goto" slew... 'cuz the scope has no clue what it is pointing at at this stage and your "goto" slew will be completely wrong and probably try to run the scope into the mount.



you can turn off the scope but you dont need to to determine direction in the eyepiece -- just loosen the clutches and move the scope north south east west to see which direction a star moves.



remember, you have not done any sync/ align steps at this stage, so the scope has no idea where it is pointing, nor does it matter. polar alignment is about correct physical orientation of the mount head.



one other thing you need to learn before doing this. figure out which direction you need to turn the alt/az adjustment knobs to make the mount move east, west, up, down. when you are in the dark and your drift alignment tells you the mount is too far WEST, you need to know what direction to turn the az adjustment knobs to make the head move EAST... or too low, how do i turn the alt knob to make the head move up.



hope that helps



--- In Losmandy_users@yahoogroups.com, "ott_je" jc.ott@...> wrote:

>

>

> Thanks for the reply, I appreciate it.

>

> You said to "manually" move the mount to the stars for drift alignment. Do you actually mean to release the clutches or do you mean to manually slew to each of the two stars?

>

> Another question comes to mind. May a person turn off the Gemini to determine direction in the eyepiece or does that totally throw all adjustments out the window? Just interested to know what is done to achieve knowledge of East, West, North, South in the eyepiece.

>

> Thanks,

> Jerry.

>

>

>

>

> -- In Losmandy_users@yahoogroups.com, "lmbuck2000" lmbuck2000@> wrote:

> >

> > here is what i do...

> >

> > 1. rough polar align -- which means, level the mount, rough visual alignment of the RA axis in North-South direction (stand on the south side of the mount and "point" it north), altitude adjustment of the RA axis equal to your latitude. takes 2 minutes. if you can not see polaris, it helps to keep a compass and angle level with your gear if go to a new place. also need to know your approximate magnetic declination adjustment to correct magnetic north for true north (easy to find on the web). if you are in the same place most of the time, you only need to do the rough altitude adjustment once and eyeball true north.

> >

> > 2. use your polar axis scope to refine polar alignment (assuming you have one). takes a few minutes (once you get the hang of it) and i find this is usually within 20-30min accuracy in alt and azi. if you don't have a PAS, just naked-eye sight align through the RA axis shaft so you can see polaris (you will have to rotate the scope in DEC to align the dec axis opening with the RA shaft interior). these alignment adjustments involve alt and az adjustments to the mount head. not moving the scope in RA and DEC.

> >

> > 3. turn on the scope. dont worry about start-up, sync, etc. just put it in sidereal tracking mode (you are not going to slew to anything yet so it does not matter that the scope does not know where it is pointing)

> >

> > 4. now drift align -- search the web and you will find plenty of explanations. use a higher power eyepiece with illuminated cross hair reticle (and barlow). manually move the scope to pick your star for polar alignment -- one to the south and one to the east (ideally). here is a good explanation of the adjustments. like i said, search the web and you can find plenty more if this one is not clear.

> >

> > www.astropix.com/HTML/I_ASTROP/TRACKED/POLAR.HTM

> >

> > this usually takes me 30-40 minutes. some consider that long, i consider it peaceful.

> >

> > OK, after you do all that (if you want/need to because you plan on taking pictures), then put the mount in CWD position and cold start to begin the synchronization and model building. after doing some model building, you can use the gemini polar axis correction function for some improvement. the best alignment i have ever achieved was 1min in az and elev. most of the time it is 5-8min. by the time i do all that, an hour has gone by (and i am relaxed :-)

> >

> > if you only want visual tracking, you can probably get away with only the first step (and second without PAS). if you have a polar axis scope, throw that in too for good measure and you can probably track for an hour without losing an image from view.

> >

> > you can start even before total darkness. some bright stars are visible shortly after sundown.

> >

> >

> > >

> > > Thanks Dave for all the information,

> > >

> > > You made this statement:

> > >

> > > - "Use the Gemini polar alignment routines and/or drift

> > > align to refine the altitude and azimuth adjustment.

> > > This is the step at which you need to sweat getting

> > > as close as possible to exact alignment, depending

> > > on your tracking requirements."

> > >

> > > I apologize that I must not have made myself very clear. Since I want to do long exposure photography, I need to know HOW to drift align my system and have the ability to make accurate goto's. It seems that you must have assumed that I know how to do a drift alignment from what I've told you. That, my friend, couldn't be farther from the truth. :-) I'm merely wanting to know how to do the two star drift alignment procedure with this system and where it fits in with the modeling routine.

> > >

> >

>







----------------------------

#43872 Sep 4, 2009

Thanks very much. A great explanation. I did realize that this was all about making sure the mount head is correctly oriented. And, I'm pretty familiar with the mount's east west and elevation knobs.



Best regards,

Jerry.





--- In Losmandy_users@yahoogroups.com, "lmbuck2000" lmbuck2000@...> wrote:

>

> you can release the clutches and manually move the scope OR use slewing... just dont try to "goto" slew... 'cuz the scope has no clue what it is pointing at at this stage and your "goto" slew will be completely wrong and probably try to run the scope into the mount.

>

> you can turn off the scope but you dont need to to determine direction in the eyepiece -- just loosen the clutches and move the scope north south east west to see which direction a star moves.

>

> remember, you have not done any sync/ align steps at this stage, so the scope has no idea where it is pointing, nor does it matter. polar alignment is about correct physical orientation of the mount head.

>

> one other thing you need to learn before doing this. figure out which direction you need to turn the alt/az adjustment knobs to make the mount move east, west, up, down. when you are in the dark and your drift alignment tells you the mount is too far WEST, you need to know what direction to turn the az adjustment knobs to make the head move EAST... or too low, how do i turn the alt knob to make the head move up.

>

> hope that helps

>

>

> --- In Losmandy_users@yahoogroups.com, "ott_je" jc.ott@> wrote:

> >

> >

> > Thanks for the reply, I appreciate it.

> >

> > You said to "manually" move the mount to the stars for drift alignment. Do you actually mean to release the clutches or do you mean to manually slew to each of the two stars?

> >

> > Another question comes to mind. May a person turn off the Gemini to determine direction in the eyepiece or does that totally throw all adjustments out the window? Just interested to know what is done to achieve knowledge of East, West, North, South in the eyepiece.

> >

> > Thanks,

> > Jerry.

> >

> >

> >

> >

> > -- In Losmandy_users@yahoogroups.com, "lmbuck2000" lmbuck2000@> wrote:

> > >

> > > here is what i do...

> > >

> > > 1. rough polar align -- which means, level the mount, rough visual alignment of the RA axis in North-South direction (stand on the south side of the mount and "point" it north), altitude adjustment of the RA axis equal to your latitude. takes 2 minutes. if you can not see polaris, it helps to keep a compass and angle level with your gear if go to a new place. also need to know your approximate magnetic declination adjustment to correct magnetic north for true north (easy to find on the web). if you are in the same place most of the time, you only need to do the rough altitude adjustment once and eyeball true north.

> > >

> > > 2. use your polar axis scope to refine polar alignment (assuming you have one). takes a few minutes (once you get the hang of it) and i find this is usually within 20-30min accuracy in alt and azi. if you don't have a PAS, just naked-eye sight align through the RA axis shaft so you can see polaris (you will have to rotate the scope in DEC to align the dec axis opening with the RA shaft interior). these alignment adjustments involve alt and az adjustments to the mount head. not moving the scope in RA and DEC.

> > >

> > > 3. turn on the scope. dont worry about start-up, sync, etc. just put it in sidereal tracking mode (you are not going to slew to anything yet so it does not matter that the scope does not know where it is pointing)

> > >

> > > 4. now drift align -- search the web and you will find plenty of explanations. use a higher power eyepiece with illuminated cross hair reticle (and barlow). manually move the scope to pick your star for polar alignment -- one to the south and one to the east (ideally). here is a good explanation of the adjustments. like i said, search the web and you can find plenty more if this one is not clear.

> > >

> > > www.astropix.com/HTML/I_ASTROP/TRACKED/POLAR.HTM

> > >

> > > this usually takes me 30-40 minutes. some consider that long, i consider it peaceful.

> > >

> > > OK, after you do all that (if you want/need to because you plan on taking pictures), then put the mount in CWD position and cold start to begin the synchronization and model building. after doing some model building, you can use the gemini polar axis correction function for some improvement. the best alignment i have ever achieved was 1min in az and elev. most of the time it is 5-8min. by the time i do all that, an hour has gone by (and i am relaxed :-)

> > >

> > > if you only want visual tracking, you can probably get away with only the first step (and second without PAS). if you have a polar axis scope, throw that in too for good measure and you can probably track for an hour without losing an image from view.

> > >

> > > you can start even before total darkness. some bright stars are visible shortly after sundown.

> > >

> > >

> > > >

> > > > Thanks Dave for all the information,

> > > >

> > > > You made this statement:

> > > >

> > > > - "Use the Gemini polar alignment routines and/or drift

> > > > align to refine the altitude and azimuth adjustment.

> > > > This is the step at which you need to sweat getting

> > > > as close as possible to exact alignment, depending

> > > > on your tracking requirements."

> > > >

> > > > I apologize that I must not have made myself very clear. Since I want to do long exposure photography, I need to know HOW to drift align my system and have the ability to make accurate goto's. It seems that you must have assumed that I know how to do a drift alignment from what I've told you. That, my friend, couldn't be farther from the truth. :-) I'm merely wanting to know how to do the two star drift alignment procedure with this system and where it fits in with the modeling routine.

> > > >

> > >

> >

>







----------------------------

#43880 Sep 6, 2009

Hi - been following the mail trail here. One thing I have found that

helps, is to take a piece of blue masking tape (the kind that doesn't

stick too hard), and mark the CWD position on the mount with the two

edges of the tape so they line up edge on. This mean you can get to CWD

as a pretty reliable same spot each time. I use a MI250 mount so have

no idea where to tell you to put the tape on the G11.

Good luck

Loren Banbury.



d_kodama wrote: >

>

> Sorry I did not reply sooner, but it looks like you're in good shape.

>

> To clarify my statement about the alignment step, you do need to keep

> the clutches tight if you are going to be polar aligning using the

> Gemini polar alignment routines. If you are just using drift alignment

> as "lmbuck2000" described, you can release clutches and push the scope

> over to the alignment star. Just make sure you do a cold start with

> the counterweight down before starting to use Gemini go-to slews.

>

> Dave

>

> --- In Losmandy_users@yahoogroups.com

> mailto:Losmandy_users%40yahoogroups.com>, "ott_je" jc.ott@...> wrote:

> >

> >

> > Thanks very much. A great explanation. I did realize that this was

> all about making sure the mount head is correctly oriented. And, I'm

> pretty familiar with the mount's east west and elevation knobs.

> >

> > Best regards,

> > Jerry.

> >

> >

> >

> > --- In Losmandy_users@yahoogroups.com

> mailto:Losmandy_users%40yahoogroups.com>, "lmbuck2000" lmbuck2000@>

> wrote:

> > >

> > > you can release the clutches and manually move the scope OR use

> slewing... just dont try to "goto" slew... 'cuz the scope has no clue

> what it is pointing at at this stage and your "goto" slew will be

> completely wrong and probably try to run the scope into the mount.

> > >

> > > you can turn off the scope but you dont need to to determine

> direction in the eyepiece -- just loosen the clutches and move the

> scope north south east west to see which direction a star moves.

> > >

> > > remember, you have not done any sync/ align steps at this stage,

> so the scope has no idea where it is pointing, nor does it matter.

> polar alignment is about correct physical orientation of the mount head.

> > >

> > > one other thing you need to learn before doing this. figure out

> which direction you need to turn the alt/az adjustment knobs to make

> the mount move east, west, up, down. when you are in the dark and your

> drift alignment tells you the mount is too far WEST, you need to know

> what direction to turn the az adjustment knobs to make the head move

> EAST... or too low, how do i turn the alt knob to make the head move up.

> > >

> > > hope that helps

> > >

> > >

> > > --- In Losmandy_users@yahoogroups.com

> mailto:Losmandy_users%40yahoogroups.com>, "ott_je" jc.ott@> wrote:

> > > >

> > > >

> > > > Thanks for the reply, I appreciate it.

> > > >

> > > > You said to "manually" move the mount to the stars for drift

> alignment. Do you actually mean to release the clutches or do you mean

> to manually slew to each of the two stars?

> > > >

> > > > Another question comes to mind. May a person turn off the Gemini

> to determine direction in the eyepiece or does that totally throw all

> adjustments out the window? Just interested to know what is done to

> achieve knowledge of East, West, North, South in the eyepiece.

> > > >

> > > > Thanks,

> > > > Jerry.

> > > >

> > > >

> > > >

> > > >

> > > > -- In Losmandy_users@yahoogroups.com

> mailto:Losmandy_users%40yahoogroups.com>, "lmbuck2000" lmbuck2000@>

> wrote:

> > > > >

> > > > > here is what i do...

> > > > >

> > > > > 1. rough polar align -- which means, level the mount, rough

> visual alignment of the RA axis in North-South direction (stand on the

> south side of the mount and "point" it north), altitude adjustment of

> the RA axis equal to your latitude. takes 2 minutes. if you can not

> see polaris, it helps to keep a compass and angle level with your gear

> if go to a new place. also need to know your approximate magnetic

> declination adjustment to correct magnetic north for true north (easy

> to find on the web). if you are in the same place most of the time,

> you only need to do the rough altitude adjustment once and eyeball

> true north.

> > > > >

> > > > > 2. use your polar axis scope to refine polar alignment

> (assuming you have one). takes a few minutes (once you get the hang of

> it) and i find this is usually within 20-30min accuracy in alt and

> azi. if you don't have a PAS, just naked-eye sight align through the

> RA axis shaft so you can see polaris (you will have to rotate the

> scope in DEC to align the dec axis opening with the RA shaft

> interior). these alignment adjustments involve alt and az adjustments

> to the mount head. not moving the scope in RA and DEC.

> > > > >

> > > > > 3. turn on the scope. dont worry about start-up, sync, etc.

> just put it in sidereal tracking mode (you are not going to slew to

> anything yet so it does not matter that the scope does not know where

> it is pointing)

> > > > >

> > > > > 4. now drift align -- search the web and you will find plenty

> of explanations. use a higher power eyepiece with illuminated cross

> hair reticle (and barlow). manually move the scope to pick your star

> for polar alignment -- one to the south and one to the east (ideally).

> here is a good explanation of the adjustments. like i said, search the

> web and you can find plenty more if this one is not clear.

> > > > >

> > > > > www.astropix.com/HTML/I_ASTROP/TRACKED/POLAR.HTM

> www.astropix.com/HTML/I_ASTROP/TRACKED/POLAR.HTM>

> > > > >

> > > > > this usually takes me 30-40 minutes. some consider that long,

> i consider it peaceful.

> > > > >

> > > > > OK, after you do all that (if you want/need to because you

> plan on taking pictures), then put the mount in CWD position and cold

> start to begin the synchronization and model building. after doing

> some model building, you can use the gemini polar axis correction

> function for some improvement. the best alignment i have ever achieved

> was 1min in az and elev. most of the time it is 5-8min. by the time i

> do all that, an hour has gone by (and i am relaxed :-)

> > > > >

> > > > > if you only want visual tracking, you can probably get away

> with only the first step (and second without PAS). if you have a polar

> axis scope, throw that in too for good measure and you can probably

> track for an hour without losing an image from view.

> > > > >

> > > > > you can start even before total darkness. some bright stars

> are visible shortly after sundown.

> > > > >

> > > > >

> > > > > >

> > > > > > Thanks Dave for all the information,

> > > > > >

> > > > > > You made this statement:

> > > > > >

> > > > > > - "Use the Gemini polar alignment routines and/or drift

> > > > > > align to refine the altitude and azimuth adjustment.

> > > > > > This is the step at which you need to sweat getting

> > > > > > as close as possible to exact alignment, depending

> > > > > > on your tracking requirements."

> > > > > >

> > > > > > I apologize that I must not have made myself very clear.

> Since I want to do long exposure photography, I need to know HOW to

> drift align my system and have the ability to make accurate goto's. It

> seems that you must have assumed that I know how to do a drift

> alignment from what I've told you. That, my friend, couldn't be

> farther from the truth. :-) I'm merely wanting to know how to do the

> two star drift alignment procedure with this system and where it fits

> in with the modeling routine.

> > > > > >

> > > > >

> > > >

> > >

> >

>

>







----------------------------

#43884 Sep 7, 2009

Thanks very much Dave,



The information I've received from you and others on this subject will be of great help when I align my scope.



Thanks,

Jerry.



--- In Losmandy_users@yahoogroups.com, "d_kodama" kodama@...> wrote:

>

> Sorry I did not reply sooner, but it looks like you're in good shape.

>

> To clarify my statement about the alignment step, you do need to keep the clutches tight if you are going to be polar aligning using the Gemini polar alignment routines. If you are just using drift alignment as "lmbuck2000" described, you can release clutches and push the scope over to the alignment star. Just make sure you do a cold start with the counterweight down before starting to use Gemini go-to slews.

>

> Dave

>

>

> --- In Losmandy_users@yahoogroups.com, "ott_je" jc.ott@> wrote:

> >

> >

> > Thanks very much. A great explanation. I did realize that this was all about making sure the mount head is correctly oriented. And, I'm pretty familiar with the mount's east west and elevation knobs.

> >

> > Best regards,

> > Jerry.

> >

> >

> >

> > --- In Losmandy_users@yahoogroups.com, "lmbuck2000" lmbuck2000@> wrote:

> > >

> > > you can release the clutches and manually move the scope OR use slewing... just dont try to "goto" slew... 'cuz the scope has no clue what it is pointing at at this stage and your "goto" slew will be completely wrong and probably try to run the scope into the mount.

> > >

> > > you can turn off the scope but you dont need to to determine direction in the eyepiece -- just loosen the clutches and move the scope north south east west to see which direction a star moves.

> > >

> > > remember, you have not done any sync/ align steps at this stage, so the scope has no idea where it is pointing, nor does it matter. polar alignment is about correct physical orientation of the mount head.

> > >

> > > one other thing you need to learn before doing this. figure out which direction you need to turn the alt/az adjustment knobs to make the mount move east, west, up, down. when you are in the dark and your drift alignment tells you the mount is too far WEST, you need to know what direction to turn the az adjustment knobs to make the head move EAST... or too low, how do i turn the alt knob to make the head move up.

> > >

> > > hope that helps

> > >

> > >

> > > --- In Losmandy_users@yahoogroups.com, "ott_je" jc.ott@> wrote:

> > > >

> > > >

> > > > Thanks for the reply, I appreciate it.

> > > >

> > > > You said to "manually" move the mount to the stars for drift alignment. Do you actually mean to release the clutches or do you mean to manually slew to each of the two stars?

> > > >

> > > > Another question comes to mind. May a person turn off the Gemini to determine direction in the eyepiece or does that totally throw all adjustments out the window? Just interested to know what is done to achieve knowledge of East, West, North, South in the eyepiece.

> > > >

> > > > Thanks,

> > > > Jerry.

> > > >

> > > >

> > > >

> > > >

> > > > -- In Losmandy_users@yahoogroups.com, "lmbuck2000" lmbuck2000@> wrote:

> > > > >

> > > > > here is what i do...

> > > > >

> > > > > 1. rough polar align -- which means, level the mount, rough visual alignment of the RA axis in North-South direction (stand on the south side of the mount and "point" it north), altitude adjustment of the RA axis equal to your latitude. takes 2 minutes. if you can not see polaris, it helps to keep a compass and angle level with your gear if go to a new place. also need to know your approximate magnetic declination adjustment to correct magnetic north for true north (easy to find on the web). if you are in the same place most of the time, you only need to do the rough altitude adjustment once and eyeball true north.

> > > > >

> > > > > 2. use your polar axis scope to refine polar alignment (assuming you have one). takes a few minutes (once you get the hang of it) and i find this is usually within 20-30min accuracy in alt and azi. if you don't have a PAS, just naked-eye sight align through the RA axis shaft so you can see polaris (you will have to rotate the scope in DEC to align the dec axis opening with the RA shaft interior). these alignment adjustments involve alt and az adjustments to the mount head. not moving the scope in RA and DEC.

> > > > >

> > > > > 3. turn on the scope. dont worry about start-up, sync, etc. just put it in sidereal tracking mode (you are not going to slew to anything yet so it does not matter that the scope does not know where it is pointing)

> > > > >

> > > > > 4. now drift align -- search the web and you will find plenty of explanations. use a higher power eyepiece with illuminated cross hair reticle (and barlow). manually move the scope to pick your star for polar alignment -- one to the south and one to the east (ideally). here is a good explanation of the adjustments. like i said, search the web and you can find plenty more if this one is not clear.

> > > > >

> > > > > www.astropix.com/HTML/I_ASTROP/TRACKED/POLAR.HTM

> > > > >

> > > > > this usually takes me 30-40 minutes. some consider that long, i consider it peaceful.

> > > > >

> > > > > OK, after you do all that (if you want/need to because you plan on taking pictures), then put the mount in CWD position and cold start to begin the synchronization and model building. after doing some model building, you can use the gemini polar axis correction function for some improvement. the best alignment i have ever achieved was 1min in az and elev. most of the time it is 5-8min. by the time i do all that, an hour has gone by (and i am relaxed :-)

> > > > >

> > > > > if you only want visual tracking, you can probably get away with only the first step (and second without PAS). if you have a polar axis scope, throw that in too for good measure and you can probably track for an hour without losing an image from view.

> > > > >

> > > > > you can start even before total darkness. some bright stars are visible shortly after sundown.

> > > > >

> > > > >

> > > > > >

> > > > > > Thanks Dave for all the information,

> > > > > >

> > > > > > You made this statement:

> > > > > >

> > > > > > - "Use the Gemini polar alignment routines and/or drift

> > > > > > align to refine the altitude and azimuth adjustment.

> > > > > > This is the step at which you need to sweat getting

> > > > > > as close as possible to exact alignment, depending

> > > > > > on your tracking requirements."

> > > > > >

> > > > > > I apologize that I must not have made myself very clear. Since I want to do long exposure photography, I need to know HOW to drift align my system and have the ability to make accurate goto's. It seems that you must have assumed that I know how to do a drift alignment from what I've told you. That, my friend, couldn't be farther from the truth. :-) I'm merely wanting to know how to do the two star drift alignment procedure with this system and where it fits in with the modeling routine.

> > > > > >

> > > > >

> > > >

> > >

> >

>







----------------------------

#43885 Sep 7, 2009

Loren,



Thanks. Very interesting. Do you place the tape in a position to be able to see the counterweight shaft line up with the edge of the tape?



Jerry.

--- In Losmandy_users@yahoogroups.com, Loren lbanbury@...> wrote:

>

> Hi - been following the mail trail here. One thing I have found that

> helps, is to take a piece of blue masking tape (the kind that doesn't

> stick too hard), and mark the CWD position on the mount with the two

> edges of the tape so they line up edge on. This mean you can get to CWD

> as a pretty reliable same spot each time. I use a MI250 mount so have

> no idea where to tell you to put the tape on the G11.

> Good luck

> Loren Banbury.

>

> d_kodama wrote:

> >

> >

> > Sorry I did not reply sooner, but it looks like you're in good shape.

> >

> > To clarify my statement about the alignment step, you do need to keep

> > the clutches tight if you are going to be polar aligning using the

> > Gemini polar alignment routines. If you are just using drift alignment

> > as "lmbuck2000" described, you can release clutches and push the scope

> > over to the alignment star. Just make sure you do a cold start with

> > the counterweight down before starting to use Gemini go-to slews.

> >

> > Dave

> >

> > --- In Losmandy_users@yahoogroups.com

> > mailto:Losmandy_users%40yahoogroups.com>, "ott_je" jc.ott@> wrote:

> > >

> > >

> > > Thanks very much. A great explanation. I did realize that this was

> > all about making sure the mount head is correctly oriented. And, I'm

> > pretty familiar with the mount's east west and elevation knobs.

> > >

> > > Best regards,

> > > Jerry.

> > >

> > >

> > >

> > > --- In Losmandy_users@yahoogroups.com

> > mailto:Losmandy_users%40yahoogroups.com>, "lmbuck2000" lmbuck2000@>

> > wrote:

> > > >

> > > > you can release the clutches and manually move the scope OR use

> > slewing... just dont try to "goto" slew... 'cuz the scope has no clue

> > what it is pointing at at this stage and your "goto" slew will be

> > completely wrong and probably try to run the scope into the mount.

> > > >

> > > > you can turn off the scope but you dont need to to determine

> > direction in the eyepiece -- just loosen the clutches and move the

> > scope north south east west to see which direction a star moves.

> > > >

> > > > remember, you have not done any sync/ align steps at this stage,

> > so the scope has no idea where it is pointing, nor does it matter.

> > polar alignment is about correct physical orientation of the mount head.

> > > >

> > > > one other thing you need to learn before doing this. figure out

> > which direction you need to turn the alt/az adjustment knobs to make

> > the mount move east, west, up, down. when you are in the dark and your

> > drift alignment tells you the mount is too far WEST, you need to know

> > what direction to turn the az adjustment knobs to make the head move

> > EAST... or too low, how do i turn the alt knob to make the head move up.

> > > >

> > > > hope that helps

> > > >

> > > >

> > > > --- In Losmandy_users@yahoogroups.com

> > mailto:Losmandy_users%40yahoogroups.com>, "ott_je" jc.ott@> wrote:

> > > > >

> > > > >

> > > > > Thanks for the reply, I appreciate it.

> > > > >

> > > > > You said to "manually" move the mount to the stars for drift

> > alignment. Do you actually mean to release the clutches or do you mean

> > to manually slew to each of the two stars?

> > > > >

> > > > > Another question comes to mind. May a person turn off the Gemini

> > to determine direction in the eyepiece or does that totally throw all

> > adjustments out the window? Just interested to know what is done to

> > achieve knowledge of East, West, North, South in the eyepiece.

> > > > >

> > > > > Thanks,

> > > > > Jerry.

> > > > >

> > > > >

> > > > >

> > > > >

> > > > > -- In Losmandy_users@yahoogroups.com

> > mailto:Losmandy_users%40yahoogroups.com>, "lmbuck2000" lmbuck2000@>

> > wrote:

> > > > > >

> > > > > > here is what i do...

> > > > > >

> > > > > > 1. rough polar align -- which means, level the mount, rough

> > visual alignment of the RA axis in North-South direction (stand on the

> > south side of the mount and "point" it north), altitude adjustment of

> > the RA axis equal to your latitude. takes 2 minutes. if you can not

> > see polaris, it helps to keep a compass and angle level with your gear

> > if go to a new place. also need to know your approximate magnetic

> > declination adjustment to correct magnetic north for true north (easy

> > to find on the web). if you are in the same place most of the time,

> > you only need to do the rough altitude adjustment once and eyeball

> > true north.

> > > > > >

> > > > > > 2. use your polar axis scope to refine polar alignment

> > (assuming you have one). takes a few minutes (once you get the hang of

> > it) and i find this is usually within 20-30min accuracy in alt and

> > azi. if you don't have a PAS, just naked-eye sight align through the

> > RA axis shaft so you can see polaris (you will have to rotate the

> > scope in DEC to align the dec axis opening with the RA shaft

> > interior). these alignment adjustments involve alt and az adjustments

> > to the mount head. not moving the scope in RA and DEC.

> > > > > >

> > > > > > 3. turn on the scope. dont worry about start-up, sync, etc.

> > just put it in sidereal tracking mode (you are not going to slew to

> > anything yet so it does not matter that the scope does not know where

> > it is pointing)

> > > > > >

> > > > > > 4. now drift align -- search the web and you will find plenty

> > of explanations. use a higher power eyepiece with illuminated cross

> > hair reticle (and barlow). manually move the scope to pick your star

> > for polar alignment -- one to the south and one to the east (ideally).

> > here is a good explanation of the adjustments. like i said, search the

> > web and you can find plenty more if this one is not clear.

> > > > > >

> > > > > > www.astropix.com/HTML/I_ASTROP/TRACKED/POLAR.HTM

> > www.astropix.com/HTML/I_ASTROP/TRACKED/POLAR.HTM>

> > > > > >

> > > > > > this usually takes me 30-40 minutes. some consider that long,

> > i consider it peaceful.

> > > > > >

> > > > > > OK, after you do all that (if you want/need to because you

> > plan on taking pictures), then put the mount in CWD position and cold

> > start to begin the synchronization and model building. after doing

> > some model building, you can use the gemini polar axis correction

> > function for some improvement. the best alignment i have ever achieved

> > was 1min in az and elev. most of the time it is 5-8min. by the time i

> > do all that, an hour has gone by (and i am relaxed :-)

> > > > > >

> > > > > > if you only want visual tracking, you can probably get away

> > with only the first step (and second without PAS). if you have a polar

> > axis scope, throw that in too for good measure and you can probably

> > track for an hour without losing an image from view.

> > > > > >

> > > > > > you can start even before total darkness. some bright stars

> > are visible shortly after sundown.

> > > > > >

> > > > > >

> > > > > > >

> > > > > > > Thanks Dave for all the information,

> > > > > > >

> > > > > > > You made this statement:

> > > > > > >

> > > > > > > - "Use the Gemini polar alignment routines and/or drift

> > > > > > > align to refine the altitude and azimuth adjustment.

> > > > > > > This is the step at which you need to sweat getting

> > > > > > > as close as possible to exact alignment, depending

> > > > > > > on your tracking requirements."

> > > > > > >

> > > > > > > I apologize that I must not have made myself very clear.

> > Since I want to do long exposure photography, I need to know HOW to

> > drift align my system and have the ability to make accurate goto's. It

> > seems that you must have assumed that I know how to do a drift

> > alignment from what I've told you. That, my friend, couldn't be

> > farther from the truth. :-) I'm merely wanting to know how to do the

> > two star drift alignment procedure with this system and where it fits

> > in with the modeling routine.

> > > > > > >

> > > > > >

> > > > >

> > > >

> > >

> >

> >

>







----------------------------

#43889 Sep 7, 2009

Unfortunately on the G11 head the Dec and RA have indicator scales can

be moved. On the MI 250 those areas are fixed metal that cant be moved

so i put a piece of tape there and on the movable axes plates - thus am

able to line up the tape at the CWD point. Am not where i can take a

picture of the setup on the mi 250 or would show you. I have a G11 I am

not using but it too is not where I can get to it for a week or two. I

will keep track of the mail trail and when next i am with mounts will

take pictures on the 250 and look for a suggested location on the G11:-)

Cheers

Loren



ott_je wrote: >

>

>

> Loren,

>

> Thanks. Very interesting. Do you place the tape in a position to be

> able to see the counterweight shaft line up with the edge of the tape?

>

> Jerry.

>

> --- In Losmandy_users@yahoogroups.com

> mailto:Losmandy_users%40yahoogroups.com>, Loren lbanbury@...> wrote:

> >

> > Hi - been following the mail trail here. One thing I have found that

> > helps, is to take a piece of blue masking tape (the kind that doesn't

> > stick too hard), and mark the CWD position on the mount with the two

> > edges of the tape so they line up edge on. This mean you can get to CWD

> > as a pretty reliable same spot each time. I use a MI250 mount so have

> > no idea where to tell you to put the tape on the G11.

> > Good luck

> > Loren Banbury.

> >

> > d_kodama wrote:

> > >

> > >

> > > Sorry I did not reply sooner, but it looks like you're in good shape.

> > >

> > > To clarify my statement about the alignment step, you do need to keep

> > > the clutches tight if you are going to be polar aligning using the

> > > Gemini polar alignment routines. If you are just using drift

> alignment

> > > as "lmbuck2000" described, you can release clutches and push the

> scope

> > > over to the alignment star. Just make sure you do a cold start with

> > > the counterweight down before starting to use Gemini go-to slews.

> > >

> > > Dave

> > >

> > > --- In Losmandy_users@yahoogroups.com

> mailto:Losmandy_users%40yahoogroups.com>

> > > mailto:Losmandy_users%40yahoogroups.com>, "ott_je" jc.ott@> wrote:

> > > >

> > > >

> > > > Thanks very much. A great explanation. I did realize that this was

> > > all about making sure the mount head is correctly oriented. And, I'm

> > > pretty familiar with the mount's east west and elevation knobs.

> > > >

> > > > Best regards,

> > > > Jerry.

> > > >

> > > >

> > > >

> > > > --- In Losmandy_users@yahoogroups.com

> mailto:Losmandy_users%40yahoogroups.com>

> > > mailto:Losmandy_users%40yahoogroups.com>, "lmbuck2000" lmbuck2000@>

> > > wrote:

> > > > >

> > > > > you can release the clutches and manually move the scope OR use

> > > slewing... just dont try to "goto" slew... 'cuz the scope has no clue

> > > what it is pointing at at this stage and your "goto" slew will be

> > > completely wrong and probably try to run the scope into the mount.

> > > > >

> > > > > you can turn off the scope but you dont need to to determine

> > > direction in the eyepiece -- just loosen the clutches and move the

> > > scope north south east west to see which direction a star moves.

> > > > >

> > > > > remember, you have not done any sync/ align steps at this stage,

> > > so the scope has no idea where it is pointing, nor does it matter.

> > > polar alignment is about correct physical orientation of the mount

> head.

> > > > >

> > > > > one other thing you need to learn before doing this. figure out

> > > which direction you need to turn the alt/az adjustment knobs to make

> > > the mount move east, west, up, down. when you are in the dark and

> your

> > > drift alignment tells you the mount is too far WEST, you need to know

> > > what direction to turn the az adjustment knobs to make the head move

> > > EAST... or too low, how do i turn the alt knob to make the head

> move up.

> > > > >

> > > > > hope that helps

> > > > >

> > > > >

> > > > > --- In Losmandy_users@yahoogroups.com

> mailto:Losmandy_users%40yahoogroups.com>

> > > mailto:Losmandy_users%40yahoogroups.com>, "ott_je" jc.ott@> wrote:

> > > > > >

> > > > > >

> > > > > > Thanks for the reply, I appreciate it.

> > > > > >

> > > > > > You said to "manually" move the mount to the stars for drift

> > > alignment. Do you actually mean to release the clutches or do you

> mean

> > > to manually slew to each of the two stars?

> > > > > >

> > > > > > Another question comes to mind. May a person turn off the

> Gemini

> > > to determine direction in the eyepiece or does that totally throw all

> > > adjustments out the window? Just interested to know what is done to

> > > achieve knowledge of East, West, North, South in the eyepiece.

> > > > > >

> > > > > > Thanks,

> > > > > > Jerry.

> > > > > >

> > > > > >

> > > > > >

> > > > > >

> > > > > > -- In Losmandy_users@yahoogroups.com

> mailto:Losmandy_users%40yahoogroups.com>

> > > mailto:Losmandy_users%40yahoogroups.com>, "lmbuck2000" lmbuck2000@>

> > > wrote:

> > > > > > >

> > > > > > > here is what i do...

> > > > > > >

> > > > > > > 1. rough polar align -- which means, level the mount, rough

> > > visual alignment of the RA axis in North-South direction (stand on

> the

> > > south side of the mount and "point" it north), altitude adjustment of

> > > the RA axis equal to your latitude. takes 2 minutes. if you can not

> > > see polaris, it helps to keep a compass and angle level with your

> gear

> > > if go to a new place. also need to know your approximate magnetic

> > > declination adjustment to correct magnetic north for true north (easy

> > > to find on the web). if you are in the same place most of the time,

> > > you only need to do the rough altitude adjustment once and eyeball

> > > true north.

> > > > > > >

> > > > > > > 2. use your polar axis scope to refine polar alignment

> > > (assuming you have one). takes a few minutes (once you get the

> hang of

> > > it) and i find this is usually within 20-30min accuracy in alt and

> > > azi. if you don't have a PAS, just naked-eye sight align through the

> > > RA axis shaft so you can see polaris (you will have to rotate the

> > > scope in DEC to align the dec axis opening with the RA shaft

> > > interior). these alignment adjustments involve alt and az adjustments

> > > to the mount head. not moving the scope in RA and DEC.

> > > > > > >

> > > > > > > 3. turn on the scope. dont worry about start-up, sync, etc.

> > > just put it in sidereal tracking mode (you are not going to slew to

> > > anything yet so it does not matter that the scope does not know where

> > > it is pointing)

> > > > > > >

> > > > > > > 4. now drift align -- search the web and you will find plenty

> > > of explanations. use a higher power eyepiece with illuminated cross

> > > hair reticle (and barlow). manually move the scope to pick your star

> > > for polar alignment -- one to the south and one to the east

> (ideally).

> > > here is a good explanation of the adjustments. like i said, search

> the

> > > web and you can find plenty more if this one is not clear.

> > > > > > >

> > > > > > > www.astropix.com/HTML/I_ASTROP/TRACKED/POLAR.HTM

> www.astropix.com/HTML/I_ASTROP/TRACKED/POLAR.HTM>

> > > www.astropix.com/HTML/I_ASTROP/TRACKED/POLAR.HTM

> www.astropix.com/HTML/I_ASTROP/TRACKED/POLAR.HTM>>

> > > > > > >

> > > > > > > this usually takes me 30-40 minutes. some consider that long,

> > > i consider it peaceful.

> > > > > > >

> > > > > > > OK, after you do all that (if you want/need to because you

> > > plan on taking pictures), then put the mount in CWD position and cold

> > > start to begin the synchronization and model building. after doing

> > > some model building, you can use the gemini polar axis correction

> > > function for some improvement. the best alignment i have ever

> achieved

> > > was 1min in az and elev. most of the time it is 5-8min. by the time i

> > > do all that, an hour has gone by (and i am relaxed :-)

> > > > > > >

> > > > > > > if you only want visual tracking, you can probably get away

> > > with only the first step (and second without PAS). if you have a

> polar

> > > axis scope, throw that in too for good measure and you can probably

> > > track for an hour without losing an image from view.

> > > > > > >

> > > > > > > you can start even before total darkness. some bright stars

> > > are visible shortly after sundown.

> > > > > > >

> > > > > > >

> > > > > > > >

> > > > > > > > Thanks Dave for all the information,

> > > > > > > >

> > > > > > > > You made this statement:

> > > > > > > >

> > > > > > > > - "Use the Gemini polar alignment routines and/or drift

> > > > > > > > align to refine the altitude and azimuth adjustment.

> > > > > > > > This is the step at which you need to sweat getting

> > > > > > > > as close as possible to exact alignment, depending

> > > > > > > > on your tracking requirements."

> > > > > > > >

> > > > > > > > I apologize that I must not have made myself very clear.

> > > Since I want to do long exposure photography, I need to know HOW to

> > > drift align my system and have the ability to make accurate

> goto's. It

> > > seems that you must have assumed that I know how to do a drift

> > > alignment from what I've told you. That, my friend, couldn't be

> > > farther from the truth. :-) I'm merely wanting to know how to do the

> > > two star drift alignment procedure with this system and where it fits

> > > in with the modeling routine.

> > > > > > > >

> > > > > > >

> > > > > >

> > > > >

> > > >

> > >

> > >

> >

>

>







----------------------------

#43890 Sep 7, 2009

Thanks Loren.



Jerry.

--- In Losmandy_users@yahoogroups.com, Loren lbanbury@...> wrote:

>

> Unfortunately on the G11 head the Dec and RA have indicator scales can

> be moved. On the MI 250 those areas are fixed metal that cant be moved

> so i put a piece of tape there and on the movable axes plates - thus am

> able to line up the tape at the CWD point. Am not where i can take a

> picture of the setup on the mi 250 or would show you. I have a G11 I am

> not using but it too is not where I can get to it for a week or two. I

> will keep track of the mail trail and when next i am with mounts will

> take pictures on the 250 and look for a suggested location on the G11:-)

> Cheers

> Loren

>

> ott_je wrote:

> >

> >

> >

> > Loren,

> >

> > Thanks. Very interesting. Do you place the tape in a position to be

> > able to see the counterweight shaft line up with the edge of the tape?

> >

> > Jerry.

> >

> > --- In Losmandy_users@yahoogroups.com

> > mailto:Losmandy_users%40yahoogroups.com>, Loren lbanbury@> wrote:

> > >

> > > Hi - been following the mail trail here. One thing I have found that

> > > helps, is to take a piece of blue masking tape (the kind that doesn't

> > > stick too hard), and mark the CWD position on the mount with the two

> > > edges of the tape so they line up edge on. This mean you can get to CWD

> > > as a pretty reliable same spot each time. I use a MI250 mount so have

> > > no idea where to tell you to put the tape on the G11.

> > > Good luck

> > > Loren Banbury.

> > >

> > > d_kodama wrote:

> > > >

> > > >

> > > > Sorry I did not reply sooner, but it looks like you're in good shape.

> > > >

> > > > To clarify my statement about the alignment step, you do need to keep

> > > > the clutches tight if you are going to be polar aligning using the

> > > > Gemini polar alignment routines. If you are just using drift

> > alignment

> > > > as "lmbuck2000" described, you can release clutches and push the

> > scope

> > > > over to the alignment star. Just make sure you do a cold start with

> > > > the counterweight down before starting to use Gemini go-to slews.

> > > >

> > > > Dave

> > > >

> > > > --- In Losmandy_users@yahoogroups.com

> > mailto:Losmandy_users%40yahoogroups.com>

> > > > mailto:Losmandy_users%40yahoogroups.com>, "ott_je" jc.ott@> wrote:

> > > > >

> > > > >

> > > > > Thanks very much. A great explanation. I did realize that this was

> > > > all about making sure the mount head is correctly oriented. And, I'm

> > > > pretty familiar with the mount's east west and elevation knobs.

> > > > >

> > > > > Best regards,

> > > > > Jerry.

> > > > >

> > > > >

> > > > >

> > > > > --- In Losmandy_users@yahoogroups.com

> > mailto:Losmandy_users%40yahoogroups.com>

> > > > mailto:Losmandy_users%40yahoogroups.com>, "lmbuck2000" lmbuck2000@>

> > > > wrote:

> > > > > >

> > > > > > you can release the clutches and manually move the scope OR use

> > > > slewing... just dont try to "goto" slew... 'cuz the scope has no clue

> > > > what it is pointing at at this stage and your "goto" slew will be

> > > > completely wrong and probably try to run the scope into the mount.

> > > > > >

> > > > > > you can turn off the scope but you dont need to to determine

> > > > direction in the eyepiece -- just loosen the clutches and move the

> > > > scope north south east west to see which direction a star moves.

> > > > > >

> > > > > > remember, you have not done any sync/ align steps at this stage,

> > > > so the scope has no idea where it is pointing, nor does it matter.

> > > > polar alignment is about correct physical orientation of the mount

> > head.

> > > > > >

> > > > > > one other thing you need to learn before doing this. figure out

> > > > which direction you need to turn the alt/az adjustment knobs to make

> > > > the mount move east, west, up, down. when you are in the dark and

> > your

> > > > drift alignment tells you the mount is too far WEST, you need to know

> > > > what direction to turn the az adjustment knobs to make the head move

> > > > EAST... or too low, how do i turn the alt knob to make the head

> > move up.

> > > > > >

> > > > > > hope that helps

> > > > > >

> > > > > >

> > > > > > --- In Losmandy_users@yahoogroups.com

> > mailto:Losmandy_users%40yahoogroups.com>

> > > > mailto:Losmandy_users%40yahoogroups.com>, "ott_je" jc.ott@> wrote:

> > > > > > >

> > > > > > >

> > > > > > > Thanks for the reply, I appreciate it.

> > > > > > >

> > > > > > > You said to "manually" move the mount to the stars for drift

> > > > alignment. Do you actually mean to release the clutches or do you

> > mean

> > > > to manually slew to each of the two stars?

> > > > > > >

> > > > > > > Another question comes to mind. May a person turn off the

> > Gemini

> > > > to determine direction in the eyepiece or does that totally throw all

> > > > adjustments out the window? Just interested to know what is done to

> > > > achieve knowledge of East, West, North, South in the eyepiece.

> > > > > > >

> > > > > > > Thanks,

> > > > > > > Jerry.

> > > > > > >

> > > > > > >

> > > > > > >

> > > > > > >

> > > > > > > -- In Losmandy_users@yahoogroups.com

> > mailto:Losmandy_users%40yahoogroups.com>

> > > > mailto:Losmandy_users%40yahoogroups.com>, "lmbuck2000" lmbuck2000@>

> > > > wrote:

> > > > > > > >

> > > > > > > > here is what i do...

> > > > > > > >

> > > > > > > > 1. rough polar align -- which means, level the mount, rough

> > > > visual alignment of the RA axis in North-South direction (stand on

> > the

> > > > south side of the mount and "point" it north), altitude adjustment of

> > > > the RA axis equal to your latitude. takes 2 minutes. if you can not

> > > > see polaris, it helps to keep a compass and angle level with your

> > gear

> > > > if go to a new place. also need to know your approximate magnetic

> > > > declination adjustment to correct magnetic north for true north (easy

> > > > to find on the web). if you are in the same place most of the time,

> > > > you only need to do the rough altitude adjustment once and eyeball

> > > > true north.

> > > > > > > >

> > > > > > > > 2. use your polar axis scope to refine polar alignment

> > > > (assuming you have one). takes a few minutes (once you get the

> > hang of

> > > > it) and i find this is usually within 20-30min accuracy in alt and

> > > > azi. if you don't have a PAS, just naked-eye sight align through the

> > > > RA axis shaft so you can see polaris (you will have to rotate the

> > > > scope in DEC to align the dec axis opening with the RA shaft

> > > > interior). these alignment adjustments involve alt and az adjustments

> > > > to the mount head. not moving the scope in RA and DEC.

> > > > > > > >

> > > > > > > > 3. turn on the scope. dont worry about start-up, sync, etc.

> > > > just put it in sidereal tracking mode (you are not going to slew to

> > > > anything yet so it does not matter that the scope does not know where

> > > > it is pointing)

> > > > > > > >

> > > > > > > > 4. now drift align -- search the web and you will find plenty

> > > > of explanations. use a higher power eyepiece with illuminated cross

> > > > hair reticle (and barlow). manually move the scope to pick your star

> > > > for polar alignment -- one to the south and one to the east

> > (ideally).

> > > > here is a good explanation of the adjustments. like i said, search

> > the

> > > > web and you can find plenty more if this one is not clear.

> > > > > > > >

> > > > > > > > www.astropix.com/HTML/I_ASTROP/TRACKED/POLAR.HTM

> > www.astropix.com/HTML/I_ASTROP/TRACKED/POLAR.HTM>

> > > > www.astropix.com/HTML/I_ASTROP/TRACKED/POLAR.HTM

> > www.astropix.com/HTML/I_ASTROP/TRACKED/POLAR.HTM>>

> > > > > > > >

> > > > > > > > this usually takes me 30-40 minutes. some consider that long,

> > > > i consider it peaceful.

> > > > > > > >

> > > > > > > > OK, after you do all that (if you want/need to because you

> > > > plan on taking pictures), then put the mount in CWD position and cold

> > > > start to begin the synchronization and model building. after doing

> > > > some model building, you can use the gemini polar axis correction

> > > > function for some improvement. the best alignment i have ever

> > achieved

> > > > was 1min in az and elev. most of the time it is 5-8min. by the time i

> > > > do all that, an hour has gone by (and i am relaxed :-)

> > > > > > > >

> > > > > > > > if you only want visual tracking, you can probably get away

> > > > with only the first step (and second without PAS). if you have a

> > polar

> > > > axis scope, throw that in too for good measure and you can probably

> > > > track for an hour without losing an image from view.

> > > > > > > >

> > > > > > > > you can start even before total darkness. some bright stars

> > > > are visible shortly after sundown.

> > > > > > > >

> > > > > > > >

> > > > > > > > >

> > > > > > > > > Thanks Dave for all the information,

> > > > > > > > >

> > > > > > > > > You made this statement:

> > > > > > > > >

> > > > > > > > > - "Use the Gemini polar alignment routines and/or drift

> > > > > > > > > align to refine the altitude and azimuth adjustment.

> > > > > > > > > This is the step at which you need to sweat getting

> > > > > > > > > as close as possible to exact alignment, depending

> > > > > > > > > on your tracking requirements."

> > > > > > > > >

> > > > > > > > > I apologize that I must not have made myself very clear.

> > > > Since I want to do long exposure photography, I need to know HOW to

> > > > drift align my system and have the ability to make accurate

> > goto's. It

> > > > seems that you must have assumed that I know how to do a drift

> > > > alignment from what I've told you. That, my friend, couldn't be

> > > > farther from the truth. :-) I'm merely wanting to know how to do the

> > > > two star drift alignment procedure with this system and where it fits

> > > > in with the modeling routine.

> > > > > > > > >

> > > > > > > >

> > > > > > >

> > > > > >

> > > > >

> > > >

> > > >

> > >

> >

> >

>







----------------------------

#43891 Sep 7, 2009

check your normal email - i replied there

Cheers

Loren



ott_je wrote: >

>

>

> Thanks Loren.

>

> Jerry.

>

> --- In Losmandy_users@yahoogroups.com

> mailto:Losmandy_users%40yahoogroups.com>, Loren lbanbury@...> wrote:

> >

> > Unfortunately on the G11 head the Dec and RA have indicator scales can

> > be moved. On the MI 250 those areas are fixed metal that cant be moved

> > so i put a piece of tape there and on the movable axes plates - thus am

> > able to line up the tape at the CWD point. Am not where i can take a

> > picture of the setup on the mi 250 or would show you. I have a G11 I am

> > not using but it too is not where I can get to it for a week or two. I

> > will keep track of the mail trail and when next i am with mounts will

> > take pictures on the 250 and look for a suggested location on the G11:-)

> > Cheers

> > Loren

> >

> > ott_je wrote:

> > >

> > >

> > >

> > > Loren,

> > >

> > > Thanks. Very interesting. Do you place the tape in a position to be

> > > able to see the counterweight shaft line up with the edge of the tape?

> > >

> > > Jerry.

> > >

> > > --- In Losmandy_users@yahoogroups.com

> mailto:Losmandy_users%40yahoogroups.com>

> > > mailto:Losmandy_users%40yahoogroups.com>, Loren lbanbury@> wrote:

> > > >

> > > > Hi - been following the mail trail here. One thing I have found that

> > > > helps, is to take a piece of blue masking tape (the kind that

> doesn't

> > > > stick too hard), and mark the CWD position on the mount with the two

> > > > edges of the tape so they line up edge on. This mean you can get

> to CWD

> > > > as a pretty reliable same spot each time. I use a MI250 mount so

> have

> > > > no idea where to tell you to put the tape on the G11.

> > > > Good luck

> > > > Loren Banbury.

> > > >

> > > > d_kodama wrote:

> > > > >

> > > > >

> > > > > Sorry I did not reply sooner, but it looks like you're in good

> shape.

> > > > >

> > > > > To clarify my statement about the alignment step, you do need

> to keep

> > > > > the clutches tight if you are going to be polar aligning using the

> > > > > Gemini polar alignment routines. If you are just using drift

> > > alignment

> > > > > as "lmbuck2000" described, you can release clutches and push the

> > > scope

> > > > > over to the alignment star. Just make sure you do a cold start

> with

> > > > > the counterweight down before starting to use Gemini go-to slews.

> > > > >

> > > > > Dave

> > > > >

> > > > > --- In Losmandy_users@yahoogroups.com

> mailto:Losmandy_users%40yahoogroups.com>

> > > mailto:Losmandy_users%40yahoogroups.com>

> > > > > mailto:Losmandy_users%40yahoogroups.com>, "ott_je" jc.ott@>

> wrote:

> > > > > >

> > > > > >

> > > > > > Thanks very much. A great explanation. I did realize that

> this was

> > > > > all about making sure the mount head is correctly oriented.

> And, I'm

> > > > > pretty familiar with the mount's east west and elevation knobs.

> > > > > >

> > > > > > Best regards,

> > > > > > Jerry.

> > > > > >

> > > > > >

> > > > > >

> > > > > > --- In Losmandy_users@yahoogroups.com

> mailto:Losmandy_users%40yahoogroups.com>

> > > mailto:Losmandy_users%40yahoogroups.com>

> > > > > mailto:Losmandy_users%40yahoogroups.com>, "lmbuck2000"

> lmbuck2000@>

> > > > > wrote:

> > > > > > >

> > > > > > > you can release the clutches and manually move the scope

> OR use

> > > > > slewing... just dont try to "goto" slew... 'cuz the scope has

> no clue

> > > > > what it is pointing at at this stage and your "goto" slew will be

> > > > > completely wrong and probably try to run the scope into the mount.

> > > > > > >

> > > > > > > you can turn off the scope but you dont need to to determine

> > > > > direction in the eyepiece -- just loosen the clutches and move the

> > > > > scope north south east west to see which direction a star moves.

> > > > > > >

> > > > > > > remember, you have not done any sync/ align steps at this

> stage,

> > > > > so the scope has no idea where it is pointing, nor does it matter.

> > > > > polar alignment is about correct physical orientation of the

> mount

> > > head.

> > > > > > >

> > > > > > > one other thing you need to learn before doing this.

> figure out

> > > > > which direction you need to turn the alt/az adjustment knobs

> to make

> > > > > the mount move east, west, up, down. when you are in the dark and

> > > your

> > > > > drift alignment tells you the mount is too far WEST, you need

> to know

> > > > > what direction to turn the az adjustment knobs to make the

> head move

> > > > > EAST... or too low, how do i turn the alt knob to make the head

> > > move up.

> > > > > > >

> > > > > > > hope that helps

> > > > > > >

> > > > > > >

> > > > > > > --- In Losmandy_users@yahoogroups.com

> mailto:Losmandy_users%40yahoogroups.com>

> > > mailto:Losmandy_users%40yahoogroups.com>

> > > > > mailto:Losmandy_users%40yahoogroups.com>, "ott_je" jc.ott@>

> wrote:

> > > > > > > >

> > > > > > > >

> > > > > > > > Thanks for the reply, I appreciate it.

> > > > > > > >

> > > > > > > > You said to "manually" move the mount to the stars for drift

> > > > > alignment. Do you actually mean to release the clutches or do you

> > > mean

> > > > > to manually slew to each of the two stars?

> > > > > > > >

> > > > > > > > Another question comes to mind. May a person turn off the

> > > Gemini

> > > > > to determine direction in the eyepiece or does that totally

> throw all

> > > > > adjustments out the window? Just interested to know what is

> done to

> > > > > achieve knowledge of East, West, North, South in the eyepiece.

> > > > > > > >

> > > > > > > > Thanks,

> > > > > > > > Jerry.

> > > > > > > >

> > > > > > > >

> > > > > > > >

> > > > > > > >

> > > > > > > > -- In Losmandy_users@yahoogroups.com

> mailto:Losmandy_users%40yahoogroups.com>

> > > mailto:Losmandy_users%40yahoogroups.com>

> > > > > mailto:Losmandy_users%40yahoogroups.com>, "lmbuck2000"

> lmbuck2000@>

> > > > > wrote:

> > > > > > > > >

> > > > > > > > > here is what i do...

> > > > > > > > >

> > > > > > > > > 1. rough polar align -- which means, level the mount,

> rough

> > > > > visual alignment of the RA axis in North-South direction

> (stand on

> > > the

> > > > > south side of the mount and "point" it north), altitude

> adjustment of

> > > > > the RA axis equal to your latitude. takes 2 minutes. if you

> can not

> > > > > see polaris, it helps to keep a compass and angle level with your

> > > gear

> > > > > if go to a new place. also need to know your approximate magnetic

> > > > > declination adjustment to correct magnetic north for true

> north (easy

> > > > > to find on the web). if you are in the same place most of the

> time,

> > > > > you only need to do the rough altitude adjustment once and eyeball

> > > > > true north.

> > > > > > > > >

> > > > > > > > > 2. use your polar axis scope to refine polar alignment

> > > > > (assuming you have one). takes a few minutes (once you get the

> > > hang of

> > > > > it) and i find this is usually within 20-30min accuracy in alt and

> > > > > azi. if you don't have a PAS, just naked-eye sight align

> through the

> > > > > RA axis shaft so you can see polaris (you will have to rotate the

> > > > > scope in DEC to align the dec axis opening with the RA shaft

> > > > > interior). these alignment adjustments involve alt and az

> adjustments

> > > > > to the mount head. not moving the scope in RA and DEC.

> > > > > > > > >

> > > > > > > > > 3. turn on the scope. dont worry about start-up, sync,

> etc.

> > > > > just put it in sidereal tracking mode (you are not going to

> slew to

> > > > > anything yet so it does not matter that the scope does not

> know where

> > > > > it is pointing)

> > > > > > > > >

> > > > > > > > > 4. now drift align -- search the web and you will find

> plenty

> > > > > of explanations. use a higher power eyepiece with illuminated

> cross

> > > > > hair reticle (and barlow). manually move the scope to pick

> your star

> > > > > for polar alignment -- one to the south and one to the east

> > > (ideally).

> > > > > here is a good explanation of the adjustments. like i said,

> search

> > > the

> > > > > web and you can find plenty more if this one is not clear.

> > > > > > > > >

> > > > > > > > >

> www.astropix.com/HTML/I_ASTROP/TRACKED/POLAR.HTM

> www.astropix.com/HTML/I_ASTROP/TRACKED/POLAR.HTM>

> > > www.astropix.com/HTML/I_ASTROP/TRACKED/POLAR.HTM

> www.astropix.com/HTML/I_ASTROP/TRACKED/POLAR.HTM>>

> > > > > www.astropix.com/HTML/I_ASTROP/TRACKED/POLAR.HTM

> www.astropix.com/HTML/I_ASTROP/TRACKED/POLAR.HTM>

> > > www.astropix.com/HTML/I_ASTROP/TRACKED/POLAR.HTM

> www.astropix.com/HTML/I_ASTROP/TRACKED/POLAR.HTM>>>

> > > > > > > > >

> > > > > > > > > this usually takes me 30-40 minutes. some consider

> that long,

> > > > > i consider it peaceful.

> > > > > > > > >

> > > > > > > > > OK, after you do all that (if you want/need to because you

> > > > > plan on taking pictures), then put the mount in CWD position

> and cold

> > > > > start to begin the synchronization and model building. after doing

> > > > > some model building, you can use the gemini polar axis correction

> > > > > function for some improvement. the best alignment i have ever

> > > achieved

> > > > > was 1min in az and elev. most of the time it is 5-8min. by the

> time i

> > > > > do all that, an hour has gone by (and i am relaxed :-)

> > > > > > > > >

> > > > > > > > > if you only want visual tracking, you can probably get

> away

> > > > > with only the first step (and second without PAS). if you have a

> > > polar

> > > > > axis scope, throw that in too for good measure and you can

> probably

> > > > > track for an hour without losing an image from view.

> > > > > > > > >

> > > > > > > > > you can start even before total darkness. some bright

> stars

> > > > > are visible shortly after sundown.

> > > > > > > > >

> > > > > > > > >

> > > > > > > > > >

> > > > > > > > > > Thanks Dave for all the information,

> > > > > > > > > >

> > > > > > > > > > You made this statement:

> > > > > > > > > >

> > > > > > > > > > - "Use the Gemini polar alignment routines and/or drift

> > > > > > > > > > align to refine the altitude and azimuth adjustment.

> > > > > > > > > > This is the step at which you need to sweat getting

> > > > > > > > > > as close as possible to exact alignment, depending

> > > > > > > > > > on your tracking requirements."

> > > > > > > > > >

> > > > > > > > > > I apologize that I must not have made myself very clear.

> > > > > Since I want to do long exposure photography, I need to know

> HOW to

> > > > > drift align my system and have the ability to make accurate

> > > goto's. It

> > > > > seems that you must have assumed that I know how to do a drift

> > > > > alignment from what I've told you. That, my friend, couldn't be

> > > > > farther from the truth. :-) I'm merely wanting to know how to

> do the

> > > > > two star drift alignment procedure with this system and where

> it fits

> > > > > in with the modeling routine.

> > > > > > > > > >

> > > > > > > > >

> > > > > > > >

> > > > > > >

> > > > > >

> > > > >

> > > > >

> > > >

> > >

> > >

> >

>

>







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