Re: Question about autoguiding - Jim


May 13, 2006

 


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

#24139 May 13, 2006

Well Jim,



I'm happy to report near perfect guiding last night with Maxim :o).



I want claim to victory and do a celebration dance, but I might jinx it,

plus it's too early to tell. But, nice round stars with Maxim on a 5 min

guided exposure of m13. That's all the time I got before the clouds moved

in. Just had enough time to do a cal at 0 dec and then move to the target

and shoot.



I know this is nothing special, except that I did not need or try tweaking

with params which in itself is a big departure from my experiences of the

last few weeks. Min move was at 0.00 max move at 3 secs. My guide errors

were .045 X and .042 Y RMS values with never more than .15 pixels peak to

peak using a 300mm guide scope and my main scope at 1300mm. Seeing must have

been ok because it wasn't chasing and I was using 2 sec integrations. No

ovals!!! I think I should be able to get some tighter stars by using your

min/max move values. I'll just pretend this mount has the same

characteristics as an AP mount and use your numbers and see what happens

next opportunity. Bottom line is the PE is very smooth and I'm guessing has

improved by an arcsec or so but I need to run some extended logs to be sure.



Things are looking promising but I'm not counting the chickens yet. I want

to test at different DECS and on the other side of the meridian. I'm

definitely NOT going to use DEC compensation any more. I did the calib at 0

dec within 2 mins of the meridian using a guide speed of .5x with an

aggressiveness of 7.



Once again, thanks very much for authoring such a fine paper Jim! You can't

imagine the elation I felt watching the tracking graph sit on the zero line

for nearly 90% of the exposure time!



Cheers,

Stef



P.S. You mentioned a multiple star guider plug-in in your article. I haven't

been able to locate it on the net though and was wondering if it was still

available?







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

From: MaxImDL@yahoogroups.com [mailto:MaxImDL@yahoogroups.com]On Behalf

Of mcmillanjr4221

Sent: Friday, May 12, 2006 3:27 PM

To: MaxImDL@yahoogroups.com

Subject: [MaxImDL] Re: Question about autoguiding





Hi Stef,



Glad you found some value in my paper. Good luck getting the new

mount working well.



I had to smile regarding your comment about my recommendations not

being particularly applicable to your LX200. I guess I'd take the

view that while it may not have helped your guiding all that much,

it explained what was going on. Indeed, you ended up taking my 1st

recommendation quite seriously - do everything you can to minimize

the need for making corrections. You took it to the max - e.g.

replace the mount! In fact, that's just what I did as well!



Regards,



Jim



--- In MaxImDL@yahoogroups.com, "Stef Cancelli" scancelli@...>

wrote: >

> Jim,

>

> This is a wonderful paper! I had read it last year but didn't put

too much > credence behind it because I was using an LX200GPS at the time and

your > recommendations didn't seem to apply. That mount needed aggressive

guider > correction at the expense of bloated stars. That is why I only

used it for > imaging at sub 400mm FL's.

>

> I recently up at used Tak EM200 and have been having inconsistent

guiding > results over the last few weeks. After re-reading your paper, I

decided to > partially dissemble the mount and check the mechanics. I found

that the RA > worm had more friction and stiffness around about 1/2 of it's turn

than the > other half or so. This supports some funky numbers I've seen while

doing > hours of PE analysis of tracking logs and guider logs. I have been

getting > perfectly OVAL stars oriented along the RA axis with longer 10min

exposures. > 5 min exposure were much better with only a few ruined exposures

from bad > guiding. I've adjusted the worm block so now it feels consistently

smooth > and buttery without any noticeable backlash during an entire 360

degree > rotation of the worm. This may have fixed that problem.

>

> Hopefully tonight, the clouds will clear up enough to let me test

your > recommendations with Maxim. I feel I'm at least armed with a good

> understanding of the variables - especially the overcorrection and

guide > star S/N regarding centroid calculations. I've noticed that I was

getting > much better results with very bright stars for guiding than dim

ones and I > suspected it was due to poor dynamic range.

>

> I think the S/N ratio is even more important with certain cameras.

I'm using > a DSI pro as a guider and I tell you, the stars look very ugly in

it's raw > mode with non square pixels and the interlacing clearly visible

between > rows. With it's lack of temperature regulation and sensors, it's

very > difficult to get accurate dark subtraction to clean up the stray

warm pixels > thereby confusing centroid calculations even more. Also, it takes

a min of 3 > secs to download a DSI frame using hi-speed USB and I believe

there is > latency of 1 frame. Meaning, that the downloaded frame is probably

at least > 5 secs old or longer. I have no way to confirm this except when I

use focus > mode and notice a change in focus requires me to wait an extra

frame before > I see the results of my adjutment. Guider logs show that it is a

min of 3 > secs between each exposure, no matter how short the exposure time

and I > believe those to be 1 frame older than the time stamp. I don't

believe there > is a solution to this since the DSI does not support hardware

subframes or > binning so the entire frame must be downloaded each time.

>

> I'm relying on the smoothness of tracking on this mount with very

subtle and > gentle guide correction over longer guide integrations to give me

good > results at the longer focal lengths I am trying to shoot (1300mm

up to > 1800mm).

>

> Wish me luck!

>

> cheers,

> Stef.

>

>

>

>

>

> -----Original Message-----

> From: MaxImDL@yahoogroups.com [mailto:MaxImDL@yahoogroups.com]On

Behalf > Of mcmillanjr4221

> Sent: Thursday, May 11, 2006 6:29 PM

> To: MaxImDL@yahoogroups.com

> Subject: [MaxImDL] Re: Question about autoguiding

>

>

> I'll take this a step further...

>

> I recalibrated my guider last August when I bought the rotator.

> I've since added a 6.3 FR into the imaging train. All I did then

> was manually adjust the x,y speeds to account for the FR (meaning I

> reduced the values by multiplying by 0.63). I still haven't used

> MaxIm to recalibrate. No need to. I've imaged probably 30 or more

> targets since then (5 - 10 hours/target), each at a different

camera > orientation and all over the sky. ACP automatically puts the

> correct value into MaxIm's camera angle field so guiding works

> perfectly; every target, every time. I never have to change my

> min/max/aggressiveness settings from target to target or night to

> night. (In fact, since I use ACP and do virtually all my imaging

> unattended, it's not practical to make changes anyway. The only

> thing that does change is the guide exposure length, which is

> dynamically managed by ACP to insure sufficient/optimum guide star

> SNR regardless of star brightness and/or filter.) I can honestly

> say I have not lost one image due to a guiding problem.

>

> If you've read my paper, you'll know I'm a big proponent of not

> being too aggressive with your guiding. Primarily I recommend this

> strategy to make sure you don't chase the seeing. A side benefit

of > this approach is that the accuracy of the actual calibration isn't

> all that critical since you only send a portion of the detected

> correction to the mount anyway. "Perfect" calibration isn't

> necessary if your aggressiveness is somewhere around 5. Indeed,

> striving to have perfect calibration and guiding more aggressively

> almost always ends up chasing the seeing such that results are

> inferior (meaning bloated stars).

>

> The "fly in this ointment" is when the mount has mechanical

problems > such that it requires aggressive guiding to keep up with the

> mechanical errors. In this case, you not only "chase the

mechanical > errors" but also end up chasing the seeing as well because for each

> guide cycle, you never know whether you are correcting for a

> mechanical error or a seeing-induced error. The result, at best,

is > bloated stars.

>

> That's why it's so important to do everything you can to reduce the

> mechanical errors first (meaning decent polar alignment and PEM

> training) as the first step in successful autoguiding.

>

> With regard to DEC Compensation, there is a large section in my

> paper discussing it, what it does, and the potential issues that

may > arise when using it (and/or recalibrating for each target). My

> advice is to be aware of the issues and try it both ways. It will

> be obvious whether using it improves or hurts your guiding results

> (meaning oscillations in RA).

>

> You can find my paper at:

>

> acp4.dc3.com/McMillanAutoguiding11-2005.pdf

>

> FWIW.

>

> Jim McMillan

>

>

>

> --- In MaxImDL@yahoogroups.com, Bob Denny rdenny@> wrote:

> >

> > > That is a little pearl of wisdom that I'm sure will help me. I

> have

> > > gone through the tutorials and McMillans paper and didn't see

> that.

> >

> > That's because, like Peterson, McMillan "never" recalibrates,

even > though

> > he has a rotator and a german mount! If you do it right, it's not

> necessary

> > to recal over and over. If you recal at some dec other than 0

with > the dec

> > set to 0, the cal will be valid only for points near that

> declination, and

> > you'll be forced to recal again and again and again..... :-)))

> >

> > Imagine running completely automated for weeks or more all over

> the sky

> > without needing to recalibrate the guider. Thanks to MaxIm's most

> excellent

> > design, this is possible, even with a motor rotator!!!

> >

> > -- Bob

> >

>

>

>

>

>

>

>

>

> Yahoo! Groups Links

>



















Yahoo! Groups Links







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

#24142 May 13, 2006

Oh, pardon me. Toronto. What happens if you try guiding something

in Virgo or Coma Berenice like M85? I have been guiding very well

in the M13 latitudes(36 deg Dec.), but get up around 20 deg

declination and things go downhill.

Jim Smith



--- In MaxImDL@yahoogroups.com, "Stef Cancelli" scancelli@...>

wrote: >

> Well Jim,

>

> I'm happy to report near perfect guiding last night with Maxim :o).

>

> I want claim to victory and do a celebration dance, but I might

jinx it, > plus it's too early to tell. But, nice round stars with Maxim on a

5 min > guided exposure of m13. That's all the time I got before the

clouds moved > in. Just had enough time to do a cal at 0 dec and then move to the

target > and shoot.

>

> I know this is nothing special, except that I did not need or try

tweaking > with params which in itself is a big departure from my experiences

of the > last few weeks. Min move was at 0.00 max move at 3 secs. My guide

errors > were .045 X and .042 Y RMS values with never more than .15 pixels

peak to > peak using a 300mm guide scope and my main scope at 1300mm. Seeing

must have > been ok because it wasn't chasing and I was using 2 sec

integrations. No > ovals!!! I think I should be able to get some tighter stars by

using your > min/max move values. I'll just pretend this mount has the same

> characteristics as an AP mount and use your numbers and see what

happens > next opportunity. Bottom line is the PE is very smooth and I'm

guessing has > improved by an arcsec or so but I need to run some extended logs

to be sure. >

> Things are looking promising but I'm not counting the chickens

yet. I want > to test at different DECS and on the other side of the meridian.

I'm > definitely NOT going to use DEC compensation any more. I did the

calib at 0 > dec within 2 mins of the meridian using a guide speed of .5x with

an > aggressiveness of 7.

>

> Once again, thanks very much for authoring such a fine paper Jim!

You can't > imagine the elation I felt watching the tracking graph sit on the

zero line > for nearly 90% of the exposure time!

>

> Cheers,

> Stef

>

> P.S. You mentioned a multiple star guider plug-in in your article.

I haven't > been able to locate it on the net though and was wondering if it

was still > available?

>

>

>

> -----Original Message-----

> From: MaxImDL@yahoogroups.com [mailto:MaxImDL@yahoogroups.com]On

Behalf > Of mcmillanjr4221

> Sent: Friday, May 12, 2006 3:27 PM

> To: MaxImDL@yahoogroups.com

> Subject: [MaxImDL] Re: Question about autoguiding

>

>

> Hi Stef,

>

> Glad you found some value in my paper. Good luck getting the new

> mount working well.

>

> I had to smile regarding your comment about my recommendations not

> being particularly applicable to your LX200. I guess I'd take the

> view that while it may not have helped your guiding all that much,

> it explained what was going on. Indeed, you ended up taking my 1st

> recommendation quite seriously - do everything you can to minimize

> the need for making corrections. You took it to the max - e.g.

> replace the mount! In fact, that's just what I did as well!

>

> Regards,

>

> Jim

>

> --- In MaxImDL@yahoogroups.com, "Stef Cancelli" scancelli@>

> wrote:

> >

> > Jim,

> >

> > This is a wonderful paper! I had read it last year but didn't put

> too much

> > credence behind it because I was using an LX200GPS at the time

and > your

> > recommendations didn't seem to apply. That mount needed

aggressive > guider

> > correction at the expense of bloated stars. That is why I only

> used it for

> > imaging at sub 400mm FL's.

> >

> > I recently up at used Tak EM200 and have been having

inconsistent > guiding

> > results over the last few weeks. After re-reading your paper, I

> decided to

> > partially dissemble the mount and check the mechanics. I found

> that the RA

> > worm had more friction and stiffness around about 1/2 of it's

turn > than the

> > other half or so. This supports some funky numbers I've seen

while > doing

> > hours of PE analysis of tracking logs and guider logs. I have

been > getting

> > perfectly OVAL stars oriented along the RA axis with longer 10min

> exposures.

> > 5 min exposure were much better with only a few ruined exposures

> from bad

> > guiding. I've adjusted the worm block so now it feels

consistently > smooth

> > and buttery without any noticeable backlash during an entire 360

> degree

> > rotation of the worm. This may have fixed that problem.

> >

> > Hopefully tonight, the clouds will clear up enough to let me test

> your

> > recommendations with Maxim. I feel I'm at least armed with a good

> > understanding of the variables - especially the overcorrection

and > guide

> > star S/N regarding centroid calculations. I've noticed that I was

> getting

> > much better results with very bright stars for guiding than dim

> ones and I

> > suspected it was due to poor dynamic range.

> >

> > I think the S/N ratio is even more important with certain

cameras. > I'm using

> > a DSI pro as a guider and I tell you, the stars look very ugly in

> it's raw

> > mode with non square pixels and the interlacing clearly visible

> between

> > rows. With it's lack of temperature regulation and sensors, it's

> very

> > difficult to get accurate dark subtraction to clean up the stray

> warm pixels

> > thereby confusing centroid calculations even more. Also, it takes

> a min of 3

> > secs to download a DSI frame using hi-speed USB and I believe

> there is

> > latency of 1 frame. Meaning, that the downloaded frame is

probably > at least

> > 5 secs old or longer. I have no way to confirm this except when I

> use focus

> > mode and notice a change in focus requires me to wait an extra

> frame before

> > I see the results of my adjutment. Guider logs show that it is a

> min of 3

> > secs between each exposure, no matter how short the exposure time

> and I

> > believe those to be 1 frame older than the time stamp. I don't

> believe there

> > is a solution to this since the DSI does not support hardware

> subframes or

> > binning so the entire frame must be downloaded each time.

> >

> > I'm relying on the smoothness of tracking on this mount with very

> subtle and

> > gentle guide correction over longer guide integrations to give me

> good

> > results at the longer focal lengths I am trying to shoot (1300mm

> up to

> > 1800mm).

> >

> > Wish me luck!

> >

> > cheers,

> > Stef.

> >

> >

> >

> >

> >

> > -----Original Message-----

> > From: MaxImDL@yahoogroups.com [mailto:MaxImDL@yahoogroups.com]On

> Behalf

> > Of mcmillanjr4221

> > Sent: Thursday, May 11, 2006 6:29 PM

> > To: MaxImDL@yahoogroups.com

> > Subject: [MaxImDL] Re: Question about autoguiding

> >

> >

> > I'll take this a step further...

> >

> > I recalibrated my guider last August when I bought the rotator.

> > I've since added a 6.3 FR into the imaging train. All I did then

> > was manually adjust the x,y speeds to account for the FR

(meaning I > > reduced the values by multiplying by 0.63). I still haven't used

> > MaxIm to recalibrate. No need to. I've imaged probably 30 or

more > > targets since then (5 - 10 hours/target), each at a different

> camera

> > orientation and all over the sky. ACP automatically puts the

> > correct value into MaxIm's camera angle field so guiding works

> > perfectly; every target, every time. I never have to change my

> > min/max/aggressiveness settings from target to target or night to

> > night. (In fact, since I use ACP and do virtually all my imaging

> > unattended, it's not practical to make changes anyway. The only

> > thing that does change is the guide exposure length, which is

> > dynamically managed by ACP to insure sufficient/optimum guide

star > > SNR regardless of star brightness and/or filter.) I can honestly

> > say I have not lost one image due to a guiding problem.

> >

> > If you've read my paper, you'll know I'm a big proponent of not

> > being too aggressive with your guiding. Primarily I recommend

this > > strategy to make sure you don't chase the seeing. A side benefit

> of

> > this approach is that the accuracy of the actual calibration

isn't > > all that critical since you only send a portion of the detected

> > correction to the mount anyway. "Perfect" calibration isn't

> > necessary if your aggressiveness is somewhere around 5. Indeed,

> > striving to have perfect calibration and guiding more

aggressively > > almost always ends up chasing the seeing such that results are

> > inferior (meaning bloated stars).

> >

> > The "fly in this ointment" is when the mount has mechanical

> problems

> > such that it requires aggressive guiding to keep up with the

> > mechanical errors. In this case, you not only "chase the

> mechanical

> > errors" but also end up chasing the seeing as well because for

each > > guide cycle, you never know whether you are correcting for a

> > mechanical error or a seeing-induced error. The result, at best,

> is

> > bloated stars.

> >

> > That's why it's so important to do everything you can to reduce

the > > mechanical errors first (meaning decent polar alignment and PEM

> > training) as the first step in successful autoguiding.

> >

> > With regard to DEC Compensation, there is a large section in my

> > paper discussing it, what it does, and the potential issues that

> may

> > arise when using it (and/or recalibrating for each target). My

> > advice is to be aware of the issues and try it both ways. It

will > > be obvious whether using it improves or hurts your guiding

results > > (meaning oscillations in RA).

> >

> > You can find my paper at:

> >

> > acp4.dc3.com/McMillanAutoguiding11-2005.pdf

> >

> > FWIW.

> >

> > Jim McMillan

> >

> >

> >

> > --- In MaxImDL@yahoogroups.com, Bob Denny rdenny@> wrote:

> > >

> > > > That is a little pearl of wisdom that I'm sure will help

me. I > > have

> > > > gone through the tutorials and McMillans paper and didn't see

> > that.

> > >

> > > That's because, like Peterson, McMillan "never" recalibrates,

> even

> > though

> > > he has a rotator and a german mount! If you do it right, it's

not > > necessary

> > > to recal over and over. If you recal at some dec other than 0

> with

> > the dec

> > > set to 0, the cal will be valid only for points near that

> > declination, and

> > > you'll be forced to recal again and again and again..... :-)))

> > >

> > > Imagine running completely automated for weeks or more all over

> > the sky

> > > without needing to recalibrate the guider. Thanks to MaxIm's

most > > excellent

> > > design, this is possible, even with a motor rotator!!!

> > >

> > > -- Bob

> > >

> >

> >

> >

> >

> >

> >

> >

> >

> > Yahoo! Groups Links

> >

>

>

>

>

>

>

>

>

>

> Yahoo! Groups Links

>







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

#24143 May 13, 2006

Stef,

What is your location?

Jim smith

--- In MaxImDL@yahoogroups.com, "Stef Cancelli" scancelli@...>

wrote: >

> Well Jim,

>

> I'm happy to report near perfect guiding last night with Maxim :o).

>

> I want claim to victory and do a celebration dance, but I might

jinx it, > plus it's too early to tell. But, nice round stars with Maxim on a

5 min > guided exposure of m13. That's all the time I got before the

clouds moved > in. Just had enough time to do a cal at 0 dec and then move to the

target > and shoot.

>

> I know this is nothing special, except that I did not need or try

tweaking > with params which in itself is a big departure from my experiences

of the > last few weeks. Min move was at 0.00 max move at 3 secs. My guide

errors > were .045 X and .042 Y RMS values with never more than .15 pixels

peak to > peak using a 300mm guide scope and my main scope at 1300mm. Seeing

must have > been ok because it wasn't chasing and I was using 2 sec

integrations. No > ovals!!! I think I should be able to get some tighter stars by

using your > min/max move values. I'll just pretend this mount has the same

> characteristics as an AP mount and use your numbers and see what

happens > next opportunity. Bottom line is the PE is very smooth and I'm

guessing has > improved by an arcsec or so but I need to run some extended logs

to be sure. >

> Things are looking promising but I'm not counting the chickens

yet. I want > to test at different DECS and on the other side of the meridian.

I'm > definitely NOT going to use DEC compensation any more. I did the

calib at 0 > dec within 2 mins of the meridian using a guide speed of .5x with

an > aggressiveness of 7.

>

> Once again, thanks very much for authoring such a fine paper Jim!

You can't > imagine the elation I felt watching the tracking graph sit on the

zero line > for nearly 90% of the exposure time!

>

> Cheers,

> Stef

>

> P.S. You mentioned a multiple star guider plug-in in your article.

I haven't > been able to locate it on the net though and was wondering if it

was still > available?

>

>

>

> -----Original Message-----

> From: MaxImDL@yahoogroups.com [mailto:MaxImDL@yahoogroups.com]On

Behalf > Of mcmillanjr4221

> Sent: Friday, May 12, 2006 3:27 PM

> To: MaxImDL@yahoogroups.com

> Subject: [MaxImDL] Re: Question about autoguiding

>

>

> Hi Stef,

>

> Glad you found some value in my paper. Good luck getting the new

> mount working well.

>

> I had to smile regarding your comment about my recommendations not

> being particularly applicable to your LX200. I guess I'd take the

> view that while it may not have helped your guiding all that much,

> it explained what was going on. Indeed, you ended up taking my 1st

> recommendation quite seriously - do everything you can to minimize

> the need for making corrections. You took it to the max - e.g.

> replace the mount! In fact, that's just what I did as well!

>

> Regards,

>

> Jim

>

> --- In MaxImDL@yahoogroups.com, "Stef Cancelli" scancelli@>

> wrote:

> >

> > Jim,

> >

> > This is a wonderful paper! I had read it last year but didn't put

> too much

> > credence behind it because I was using an LX200GPS at the time

and > your

> > recommendations didn't seem to apply. That mount needed

aggressive > guider

> > correction at the expense of bloated stars. That is why I only

> used it for

> > imaging at sub 400mm FL's.

> >

> > I recently up at used Tak EM200 and have been having

inconsistent > guiding

> > results over the last few weeks. After re-reading your paper, I

> decided to

> > partially dissemble the mount and check the mechanics. I found

> that the RA

> > worm had more friction and stiffness around about 1/2 of it's

turn > than the

> > other half or so. This supports some funky numbers I've seen

while > doing

> > hours of PE analysis of tracking logs and guider logs. I have

been > getting

> > perfectly OVAL stars oriented along the RA axis with longer 10min

> exposures.

> > 5 min exposure were much better with only a few ruined exposures

> from bad

> > guiding. I've adjusted the worm block so now it feels

consistently > smooth

> > and buttery without any noticeable backlash during an entire 360

> degree

> > rotation of the worm. This may have fixed that problem.

> >

> > Hopefully tonight, the clouds will clear up enough to let me test

> your

> > recommendations with Maxim. I feel I'm at least armed with a good

> > understanding of the variables - especially the overcorrection

and > guide

> > star S/N regarding centroid calculations. I've noticed that I was

> getting

> > much better results with very bright stars for guiding than dim

> ones and I

> > suspected it was due to poor dynamic range.

> >

> > I think the S/N ratio is even more important with certain

cameras. > I'm using

> > a DSI pro as a guider and I tell you, the stars look very ugly in

> it's raw

> > mode with non square pixels and the interlacing clearly visible

> between

> > rows. With it's lack of temperature regulation and sensors, it's

> very

> > difficult to get accurate dark subtraction to clean up the stray

> warm pixels

> > thereby confusing centroid calculations even more. Also, it takes

> a min of 3

> > secs to download a DSI frame using hi-speed USB and I believe

> there is

> > latency of 1 frame. Meaning, that the downloaded frame is

probably > at least

> > 5 secs old or longer. I have no way to confirm this except when I

> use focus

> > mode and notice a change in focus requires me to wait an extra

> frame before

> > I see the results of my adjutment. Guider logs show that it is a

> min of 3

> > secs between each exposure, no matter how short the exposure time

> and I

> > believe those to be 1 frame older than the time stamp. I don't

> believe there

> > is a solution to this since the DSI does not support hardware

> subframes or

> > binning so the entire frame must be downloaded each time.

> >

> > I'm relying on the smoothness of tracking on this mount with very

> subtle and

> > gentle guide correction over longer guide integrations to give me

> good

> > results at the longer focal lengths I am trying to shoot (1300mm

> up to

> > 1800mm).

> >

> > Wish me luck!

> >

> > cheers,

> > Stef.

> >

> >

> >

> >

> >

> > -----Original Message-----

> > From: MaxImDL@yahoogroups.com [mailto:MaxImDL@yahoogroups.com]On

> Behalf

> > Of mcmillanjr4221

> > Sent: Thursday, May 11, 2006 6:29 PM

> > To: MaxImDL@yahoogroups.com

> > Subject: [MaxImDL] Re: Question about autoguiding

> >

> >

> > I'll take this a step further...

> >

> > I recalibrated my guider last August when I bought the rotator.

> > I've since added a 6.3 FR into the imaging train. All I did then

> > was manually adjust the x,y speeds to account for the FR

(meaning I > > reduced the values by multiplying by 0.63). I still haven't used

> > MaxIm to recalibrate. No need to. I've imaged probably 30 or

more > > targets since then (5 - 10 hours/target), each at a different

> camera

> > orientation and all over the sky. ACP automatically puts the

> > correct value into MaxIm's camera angle field so guiding works

> > perfectly; every target, every time. I never have to change my

> > min/max/aggressiveness settings from target to target or night to

> > night. (In fact, since I use ACP and do virtually all my imaging

> > unattended, it's not practical to make changes anyway. The only

> > thing that does change is the guide exposure length, which is

> > dynamically managed by ACP to insure sufficient/optimum guide

star > > SNR regardless of star brightness and/or filter.) I can honestly

> > say I have not lost one image due to a guiding problem.

> >

> > If you've read my paper, you'll know I'm a big proponent of not

> > being too aggressive with your guiding. Primarily I recommend

this > > strategy to make sure you don't chase the seeing. A side benefit

> of

> > this approach is that the accuracy of the actual calibration

isn't > > all that critical since you only send a portion of the detected

> > correction to the mount anyway. "Perfect" calibration isn't

> > necessary if your aggressiveness is somewhere around 5. Indeed,

> > striving to have perfect calibration and guiding more

aggressively > > almost always ends up chasing the seeing such that results are

> > inferior (meaning bloated stars).

> >

> > The "fly in this ointment" is when the mount has mechanical

> problems

> > such that it requires aggressive guiding to keep up with the

> > mechanical errors. In this case, you not only "chase the

> mechanical

> > errors" but also end up chasing the seeing as well because for

each > > guide cycle, you never know whether you are correcting for a

> > mechanical error or a seeing-induced error. The result, at best,

> is

> > bloated stars.

> >

> > That's why it's so important to do everything you can to reduce

the > > mechanical errors first (meaning decent polar alignment and PEM

> > training) as the first step in successful autoguiding.

> >

> > With regard to DEC Compensation, there is a large section in my

> > paper discussing it, what it does, and the potential issues that

> may

> > arise when using it (and/or recalibrating for each target). My

> > advice is to be aware of the issues and try it both ways. It

will > > be obvious whether using it improves or hurts your guiding

results > > (meaning oscillations in RA).

> >

> > You can find my paper at:

> >

> > acp4.dc3.com/McMillanAutoguiding11-2005.pdf

> >

> > FWIW.

> >

> > Jim McMillan

> >

> >

> >

> > --- In MaxImDL@yahoogroups.com, Bob Denny rdenny@> wrote:

> > >

> > > > That is a little pearl of wisdom that I'm sure will help

me. I > > have

> > > > gone through the tutorials and McMillans paper and didn't see

> > that.

> > >

> > > That's because, like Peterson, McMillan "never" recalibrates,

> even

> > though

> > > he has a rotator and a german mount! If you do it right, it's

not > > necessary

> > > to recal over and over. If you recal at some dec other than 0

> with

> > the dec

> > > set to 0, the cal will be valid only for points near that

> > declination, and

> > > you'll be forced to recal again and again and again..... :-)))

> > >

> > > Imagine running completely automated for weeks or more all over

> > the sky

> > > without needing to recalibrate the guider. Thanks to MaxIm's

most > > excellent

> > > design, this is possible, even with a motor rotator!!!

> > >

> > > -- Bob

> > >

> >

> >

> >

> >

> >

> >

> >

> >

> > Yahoo! Groups Links

> >

>

>

>

>

>

>

>

>

>

> Yahoo! Groups Links

>







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

#24148 May 13, 2006

Great!



Regarding the multi-star guiding plug-in, John Winfield wrote it.

It can be found here:



winfij.homeip.net/maximdl/index.html



Hope all continues well!



Jim



--- In MaxImDL@yahoogroups.com, "Stef Cancelli" scancelli@...>

wrote: >

> Well Jim,

>

> I'm happy to report near perfect guiding last night with Maxim :o).

>

> I want claim to victory and do a celebration dance, but I might

jinx it, > plus it's too early to tell. But, nice round stars with Maxim on a

5 min > guided exposure of m13. That's all the time I got before the

clouds moved > in. Just had enough time to do a cal at 0 dec and then move to the

target > and shoot.

>

> I know this is nothing special, except that I did not need or try

tweaking > with params which in itself is a big departure from my experiences

of the > last few weeks. Min move was at 0.00 max move at 3 secs. My guide

errors > were .045 X and .042 Y RMS values with never more than .15 pixels

peak to > peak using a 300mm guide scope and my main scope at 1300mm. Seeing

must have > been ok because it wasn't chasing and I was using 2 sec

integrations. No > ovals!!! I think I should be able to get some tighter stars by

using your > min/max move values. I'll just pretend this mount has the same

> characteristics as an AP mount and use your numbers and see what

happens > next opportunity. Bottom line is the PE is very smooth and I'm

guessing has > improved by an arcsec or so but I need to run some extended logs

to be sure. >

> Things are looking promising but I'm not counting the chickens

yet. I want > to test at different DECS and on the other side of the meridian.

I'm > definitely NOT going to use DEC compensation any more. I did the

calib at 0 > dec within 2 mins of the meridian using a guide speed of .5x with

an > aggressiveness of 7.

>

> Once again, thanks very much for authoring such a fine paper Jim!

You can't > imagine the elation I felt watching the tracking graph sit on the

zero line > for nearly 90% of the exposure time!

>

> Cheers,

> Stef

>

> P.S. You mentioned a multiple star guider plug-in in your article.

I haven't > been able to locate it on the net though and was wondering if it

was still > available?

>

>

>

> -----Original Message-----

> From: MaxImDL@yahoogroups.com [mailto:MaxImDL@yahoogroups.com]On

Behalf > Of mcmillanjr4221

> Sent: Friday, May 12, 2006 3:27 PM

> To: MaxImDL@yahoogroups.com

> Subject: [MaxImDL] Re: Question about autoguiding

>

>

> Hi Stef,

>

> Glad you found some value in my paper. Good luck getting the new

> mount working well.

>

> I had to smile regarding your comment about my recommendations not

> being particularly applicable to your LX200. I guess I'd take the

> view that while it may not have helped your guiding all that much,

> it explained what was going on. Indeed, you ended up taking my 1st

> recommendation quite seriously - do everything you can to minimize

> the need for making corrections. You took it to the max - e.g.

> replace the mount! In fact, that's just what I did as well!

>

> Regards,

>

> Jim

>

> --- In MaxImDL@yahoogroups.com, "Stef Cancelli" scancelli@>

> wrote:

> >

> > Jim,

> >

> > This is a wonderful paper! I had read it last year but didn't put

> too much

> > credence behind it because I was using an LX200GPS at the time

and > your

> > recommendations didn't seem to apply. That mount needed

aggressive > guider

> > correction at the expense of bloated stars. That is why I only

> used it for

> > imaging at sub 400mm FL's.

> >

> > I recently up at used Tak EM200 and have been having

inconsistent > guiding

> > results over the last few weeks. After re-reading your paper, I

> decided to

> > partially dissemble the mount and check the mechanics. I found

> that the RA

> > worm had more friction and stiffness around about 1/2 of it's

turn > than the

> > other half or so. This supports some funky numbers I've seen

while > doing

> > hours of PE analysis of tracking logs and guider logs. I have

been > getting

> > perfectly OVAL stars oriented along the RA axis with longer 10min

> exposures.

> > 5 min exposure were much better with only a few ruined exposures

> from bad

> > guiding. I've adjusted the worm block so now it feels

consistently > smooth

> > and buttery without any noticeable backlash during an entire 360

> degree

> > rotation of the worm. This may have fixed that problem.

> >

> > Hopefully tonight, the clouds will clear up enough to let me test

> your

> > recommendations with Maxim. I feel I'm at least armed with a good

> > understanding of the variables - especially the overcorrection

and > guide

> > star S/N regarding centroid calculations. I've noticed that I was

> getting

> > much better results with very bright stars for guiding than dim

> ones and I

> > suspected it was due to poor dynamic range.

> >

> > I think the S/N ratio is even more important with certain

cameras. > I'm using

> > a DSI pro as a guider and I tell you, the stars look very ugly in

> it's raw

> > mode with non square pixels and the interlacing clearly visible

> between

> > rows. With it's lack of temperature regulation and sensors, it's

> very

> > difficult to get accurate dark subtraction to clean up the stray

> warm pixels

> > thereby confusing centroid calculations even more. Also, it takes

> a min of 3

> > secs to download a DSI frame using hi-speed USB and I believe

> there is

> > latency of 1 frame. Meaning, that the downloaded frame is

probably > at least

> > 5 secs old or longer. I have no way to confirm this except when I

> use focus

> > mode and notice a change in focus requires me to wait an extra

> frame before

> > I see the results of my adjutment. Guider logs show that it is a

> min of 3

> > secs between each exposure, no matter how short the exposure time

> and I

> > believe those to be 1 frame older than the time stamp. I don't

> believe there

> > is a solution to this since the DSI does not support hardware

> subframes or

> > binning so the entire frame must be downloaded each time.

> >

> > I'm relying on the smoothness of tracking on this mount with very

> subtle and

> > gentle guide correction over longer guide integrations to give me

> good

> > results at the longer focal lengths I am trying to shoot (1300mm

> up to

> > 1800mm).

> >

> > Wish me luck!

> >

> > cheers,

> > Stef.

> >

> >

> >

> >

> >

> > -----Original Message-----

> > From: MaxImDL@yahoogroups.com [mailto:MaxImDL@yahoogroups.com]On

> Behalf

> > Of mcmillanjr4221

> > Sent: Thursday, May 11, 2006 6:29 PM

> > To: MaxImDL@yahoogroups.com

> > Subject: [MaxImDL] Re: Question about autoguiding

> >

> >

> > I'll take this a step further...

> >

> > I recalibrated my guider last August when I bought the rotator.

> > I've since added a 6.3 FR into the imaging train. All I did then

> > was manually adjust the x,y speeds to account for the FR

(meaning I > > reduced the values by multiplying by 0.63). I still haven't used

> > MaxIm to recalibrate. No need to. I've imaged probably 30 or

more > > targets since then (5 - 10 hours/target), each at a different

> camera

> > orientation and all over the sky. ACP automatically puts the

> > correct value into MaxIm's camera angle field so guiding works

> > perfectly; every target, every time. I never have to change my

> > min/max/aggressiveness settings from target to target or night to

> > night. (In fact, since I use ACP and do virtually all my imaging

> > unattended, it's not practical to make changes anyway. The only

> > thing that does change is the guide exposure length, which is

> > dynamically managed by ACP to insure sufficient/optimum guide

star > > SNR regardless of star brightness and/or filter.) I can honestly

> > say I have not lost one image due to a guiding problem.

> >

> > If you've read my paper, you'll know I'm a big proponent of not

> > being too aggressive with your guiding. Primarily I recommend

this > > strategy to make sure you don't chase the seeing. A side benefit

> of

> > this approach is that the accuracy of the actual calibration

isn't > > all that critical since you only send a portion of the detected

> > correction to the mount anyway. "Perfect" calibration isn't

> > necessary if your aggressiveness is somewhere around 5. Indeed,

> > striving to have perfect calibration and guiding more

aggressively > > almost always ends up chasing the seeing such that results are

> > inferior (meaning bloated stars).

> >

> > The "fly in this ointment" is when the mount has mechanical

> problems

> > such that it requires aggressive guiding to keep up with the

> > mechanical errors. In this case, you not only "chase the

> mechanical

> > errors" but also end up chasing the seeing as well because for

each > > guide cycle, you never know whether you are correcting for a

> > mechanical error or a seeing-induced error. The result, at best,

> is

> > bloated stars.

> >

> > That's why it's so important to do everything you can to reduce

the > > mechanical errors first (meaning decent polar alignment and PEM

> > training) as the first step in successful autoguiding.

> >

> > With regard to DEC Compensation, there is a large section in my

> > paper discussing it, what it does, and the potential issues that

> may

> > arise when using it (and/or recalibrating for each target). My

> > advice is to be aware of the issues and try it both ways. It

will > > be obvious whether using it improves or hurts your guiding

results > > (meaning oscillations in RA).

> >

> > You can find my paper at:

> >

> > acp4.dc3.com/McMillanAutoguiding11-2005.pdf

> >

> > FWIW.

> >

> > Jim McMillan

> >

> >

> >

> > --- In MaxImDL@yahoogroups.com, Bob Denny rdenny@> wrote:

> > >

> > > > That is a little pearl of wisdom that I'm sure will help

me. I > > have

> > > > gone through the tutorials and McMillans paper and didn't see

> > that.

> > >

> > > That's because, like Peterson, McMillan "never" recalibrates,

> even

> > though

> > > he has a rotator and a german mount! If you do it right, it's

not > > necessary

> > > to recal over and over. If you recal at some dec other than 0

> with

> > the dec

> > > set to 0, the cal will be valid only for points near that

> > declination, and

> > > you'll be forced to recal again and again and again..... :-)))

> > >

> > > Imagine running completely automated for weeks or more all over

> > the sky

> > > without needing to recalibrate the guider. Thanks to MaxIm's

most > > excellent

> > > design, this is possible, even with a motor rotator!!!

> > >

> > > -- Bob

> > >

> >

> >

> >

> >

> >

> >

> >

> >

> > Yahoo! Groups Links

> >

>

>

>

>

>

>

>

>

>

> Yahoo! Groups Links

>







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