VintageBigBlue.org

 

Re: Ovision results - confirmed (stepper vs Gemini gearboxes?)


Sep 14, 2008

 


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

#39676 Sep 14, 2008

The weather did hold and I was able to retest with the Ovision worm.

The adjustments to the mount and the newly charged battery made all

the difference in the world. The PE is coming in just north of 3 arc

seconds. I am still having issues with programming the PEC on the

mount, but I think that may be due to backlevel ASCOM drivers on my

older laptop (which I use for PEM Pro, long story and I digress). I

put together a web page showing some of the PEM Pro screen shots and

for those of you who like to look at images, I posted a couple of

those too.



www.celestialwonders.com/equipment/OvisionVsLHPW.html



Anyone serious about longer focal length imaging without the higher

end budget would do well to consider this upgrade.



Frank

www.celestialwonders.com/equipment/OvisionVsLHPW.html



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

#39683 Sep 14, 2008

Wow, great results! Your Ovision test report was very similar to mine

as I recall. So I can only hope to see as good of results as you achieved!

Floyd --- In Losmandy_users@yahoogroups.com, "Frank Barrett" frankb@...> wrote:

>

> The weather did hold and I was able to retest with the Ovision worm.

> The adjustments to the mount and the newly charged battery made all

> the difference in the world. The PE is coming in just north of 3 arc

> seconds. I am still having issues with programming the PEC on the

> mount, but I think that may be due to backlevel ASCOM drivers on my

> older laptop (which I use for PEM Pro, long story and I digress). I

> put together a web page showing some of the PEM Pro screen shots and

> for those of you who like to look at images, I posted a couple of

> those too.

>

> www.celestialwonders.com/equipment/OvisionVsLHPW.html

>

> Anyone serious about longer focal length imaging without the higher

> end budget would do well to consider this upgrade.

>

> Frank

> www.celestialwonders.com/equipment/OvisionVsLHPW.html

>



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

#39685 Sep 14, 2008

Frank,

Nice looking frequency spectra. The 34 sec peak is probably causing

the minor elongation in your M27 shot (it looks consistent and E-W).

It just means you need to guide with ~5 sec exposures, pretty good.



You know when I guide at 2950mm efl the guider RMS residual is rarely

better than 0.6", you have 0.8" unguided...



BTW the PEC graphs you show are the artificial ones that PEMpro

created right? The second one looks way too smooth to be raw data.

Plus I would advise you to turn off the high frequency modes when

genrating the PEC curve, it's trying to model the 32sec term but that

term is non-harmonic. You really should just keep the first two

harmonics IMHO, they are really the only ones that won't do a random

phase jump on you.



Later,

EB

--- In Losmandy_users@yahoogroups.com, "Frank Barrett" frankb@...> wrote:

>

> The weather did hold and I was able to retest with the Ovision worm.

> The adjustments to the mount and the newly charged battery made all

> the difference in the world. The PE is coming in just north of 3 arc

> seconds. I am still having issues with programming the PEC on the

> mount, but I think that may be due to backlevel ASCOM drivers on my

> older laptop (which I use for PEM Pro, long story and I digress). I

> put together a web page showing some of the PEM Pro screen shots and

> for those of you who like to look at images, I posted a couple of

> those too.

>

> www.celestialwonders.com/equipment/OvisionVsLHPW.html

>

> Anyone serious about longer focal length imaging without the higher

> end budget would do well to consider this upgrade.

>

> Frank

> www.celestialwonders.com/equipment/OvisionVsLHPW.html

>



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

#39689 Sep 14, 2008

Hi Frank,



You should try out loading your raw data and using the new Frequency

Spectrum tab in PEMPro V2.5. There is a mount entry for the G11.



www.siriusimaging.com/Help/PEMProV2/frequencyspectrum.htm



-Ray

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

> From: Losmandy_users@yahoogroups.com

> [mailto:Losmandy_users@yahoogroups.com] On Behalf Of Frank Barrett

> Sent: Sunday, September 14, 2008 2:46 PM

> To: Losmandy_users@yahoogroups.com

> Subject: [Losmandy_users] Ovision results - confirmed

>

> The weather did hold and I was able to retest with the Ovision worm.

> The adjustments to the mount and the newly charged battery

> made all the difference in the world. The PE is coming in

> just north of 3 arc seconds. I am still having issues with

> programming the PEC on the mount, but I think that may be due

> to backlevel ASCOM drivers on my older laptop (which I use

> for PEM Pro, long story and I digress). I put together a web

> page showing some of the PEM Pro screen shots and for those

> of you who like to look at images, I posted a couple of those too.

>

> www.celestialwonders.com/equipment/OvisionVsLHPW.html

> www.celestialwonders.com/equipment/OvisionVsLHPW.html>

>

> Anyone serious about longer focal length imaging without the

> higher end budget would do well to consider this upgrade.

>

> Frank

> www.celestialwonders.com/equipment/OvisionVsLHPW.html

> www.celestialwonders.com/equipment/OvisionVsLHPW.html>

>

>

>

>

>







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

#39694 Sep 15, 2008

Floyd,



Your recollection is in alignment with mine...our test data were very

similar, in fact I thought your worst case numbs were slightly better

than mine. I will eat my shoe if your worm does not perform as well

or better than these results!



Frank Barrett

celestialwonders.com

--- In Losmandy_users@yahoogroups.com, "Floyd Blue" fblue@...> wrote:

>

> Wow, great results! Your Ovision test report was very similar to mine

> as I recall. So I can only hope to see as good of results as you

achieved!

> Floyd

> --- In Losmandy_users@yahoogroups.com, "Frank Barrett" frankb@> wrote:

> >

> > The weather did hold and I was able to retest with the Ovision worm.

> > The adjustments to the mount and the newly charged battery made all

> > the difference in the world. The PE is coming in just north of 3 arc

> > seconds. I am still having issues with programming the PEC on the

> > mount, but I think that may be due to backlevel ASCOM drivers on my

> > older laptop (which I use for PEM Pro, long story and I digress). I

> > put together a web page showing some of the PEM Pro screen shots and

> > for those of you who like to look at images, I posted a couple of

> > those too.

> >

> > www.celestialwonders.com/equipment/OvisionVsLHPW.html

> >

> > Anyone serious about longer focal length imaging without the higher

> > end budget would do well to consider this upgrade.

> >

> > Frank

> > www.celestialwonders.com/equipment/OvisionVsLHPW.html

> >

>



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

#39696 Sep 15, 2008

Eric,

> Nice looking frequency spectra. The 34 sec peak is probably causing

> the minor elongation in your M27 shot (it looks consistent and E-W).

> It just means you need to guide with ~5 sec exposures, pretty good.



Thanks, I do appreciate your analysis. I agree that the 32 (not 34!)

second error is the next villain to conquer and is most likely what is

causing my guider some consternation.

> You know when I guide at 2950mm efl the guider RMS residual is rarely

> better than 0.6", you have 0.8" unguided...



I am curious how you determined this?

> BTW the PEC graphs you show are the artificial ones that PEMpro

> created right? The second one looks way too smooth to be raw data.

> Plus I would advise you to turn off the high frequency modes when

> genrating the PEC curve, it's trying to model the 32sec term but that

> term is non-harmonic. You really should just keep the first two

> harmonics IMHO, they are really the only ones that won't do a random

> phase jump on you.



Yes, these are the graphs from PEMPro (artificial or not, I believe

the PE Curve downloaded to the Gemini is based on this, no?).

Consider me a PEMPro newbie. You are right about the high frequency

stuff. I did notice the high frequency undulations in the PE Curve

and speculated that this might be the 32 second error. I will have to

try this again, perhaps it is why PEC did not give me the results I

was looking for. But that may have to wait, I am having some issues

with the camera and it will likely be making a trip back to Santa

Barbara :(



Frank

celestialwonders.com



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

#39697 Sep 15, 2008

Hi Ray,



I saw that you had released 2.5 and had a mind to download and try it

out. The new frequency spectrum tab looks boss and should be very

helpful in discovering mount issues. However, my camera is

misbehaving and I will most probably have to send it back to SBIG for

repair. The last time it was 10 weeks before I got it back :( so I

may defer the trial until then.



Frank

celestialwonders.com

--- In Losmandy_users@yahoogroups.com, "Ray Gralak" rgr@...> wrote:

>

> Hi Frank,

>

> You should try out loading your raw data and using the new Frequency

> Spectrum tab in PEMPro V2.5. There is a mount entry for the G11.

>

> www.siriusimaging.com/Help/PEMProV2/frequencyspectrum.htm

>

> -Ray

>

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

> > From: Losmandy_users@yahoogroups.com

> > [mailto:Losmandy_users@yahoogroups.com] On Behalf Of Frank Barrett

> > Sent: Sunday, September 14, 2008 2:46 PM

> > To: Losmandy_users@yahoogroups.com

> > Subject: [Losmandy_users] Ovision results - confirmed

> >

> > The weather did hold and I was able to retest with the Ovision worm.

> > The adjustments to the mount and the newly charged battery

> > made all the difference in the world. The PE is coming in

> > just north of 3 arc seconds. I am still having issues with

> > programming the PEC on the mount, but I think that may be due

> > to backlevel ASCOM drivers on my older laptop (which I use

> > for PEM Pro, long story and I digress). I put together a web

> > page showing some of the PEM Pro screen shots and for those

> > of you who like to look at images, I posted a couple of those too.

> >

> > www.celestialwonders.com/equipment/OvisionVsLHPW.html

> > www.celestialwonders.com/equipment/OvisionVsLHPW.html>

> >

> > Anyone serious about longer focal length imaging without the

> > higher end budget would do well to consider this upgrade.

> >

> > Frank

> > www.celestialwonders.com/equipment/OvisionVsLHPW.html

> > www.celestialwonders.com/equipment/OvisionVsLHPW.html>

> >

> >

> >

> >

> >

>







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

#39699 Sep 15, 2008

I've added some scatter plots to my Ovision worm report. These give a

real good pictorial view of the unguided star shape. The data is

taken directly from the PEMPro logs.



celestialwonders.com/equipment/OvisionVsLHPW.html



Scroll down about half way. Enjoy.



Frank

celestialwonders.com

--- In Losmandy_users@yahoogroups.com, "Frank Barrett" frankb@...> wrote:

>

> The weather did hold and I was able to retest with the Ovision worm.

> The adjustments to the mount and the newly charged battery made all

> the difference in the world. The PE is coming in just north of 3 arc

> seconds. I am still having issues with programming the PEC on the

> mount, but I think that may be due to backlevel ASCOM drivers on my

> older laptop (which I use for PEM Pro, long story and I digress). I

> put together a web page showing some of the PEM Pro screen shots and

> for those of you who like to look at images, I posted a couple of

> those too.

>

> www.celestialwonders.com/equipment/OvisionVsLHPW.html

>

> Anyone serious about longer focal length imaging without the higher

> end budget would do well to consider this upgrade.

>

> Frank

> www.celestialwonders.com/equipment/OvisionVsLHPW.html

>



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

#39700 Sep 15, 2008

Hi Frank,

You must admit that the worm appears to be of excellent quality and

certainly meets the manufactures guarantee.

Floyd --- In Losmandy_users@yahoogroups.com, "Frank Barrett" frankb@...> wrote:

>

> Floyd,

>

> Your recollection is in alignment with mine...our test data were very

> similar, in fact I thought your worst case numbs were slightly better

> than mine. I will eat my shoe if your worm does not perform as well

> or better than these results!

>

> Frank Barrett

> celestialwonders.com

>

> --- In Losmandy_users@yahoogroups.com, "Floyd Blue" fblue@> wrote:

> >

> > Wow, great results! Your Ovision test report was very similar to mine

> > as I recall. So I can only hope to see as good of results as you

> achieved!

> > Floyd

> > --- In Losmandy_users@yahoogroups.com, "Frank Barrett" frankb@>

wrote:

> > >

> > > The weather did hold and I was able to retest with the Ovision

worm.

> > > The adjustments to the mount and the newly charged battery made all

> > > the difference in the world. The PE is coming in just north of

3 arc

> > > seconds. I am still having issues with programming the PEC on the

> > > mount, but I think that may be due to backlevel ASCOM drivers on my

> > > older laptop (which I use for PEM Pro, long story and I digress). I

> > > put together a web page showing some of the PEM Pro screen shots and

> > > for those of you who like to look at images, I posted a couple of

> > > those too.

> > >

> > > www.celestialwonders.com/equipment/OvisionVsLHPW.html

> > >

> > > Anyone serious about longer focal length imaging without the higher

> > > end budget would do well to consider this upgrade.

> > >

> > > Frank

> > > www.celestialwonders.com/equipment/OvisionVsLHPW.html

> > >

> >

>



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

#39701 Sep 15, 2008

It is time for someone to try out the Precision Gear Boxes that we

discussed earlier.

I am wondering if our friend in the UK has had any luck investigating

these?

I would certainly be willing to pay $30 each plus shipping for them if

they work. Perhaps it would pay to order a few together to avoid the

high shipping costs of individual orders. I need to send the specs

that I found on the Losmandy Gear Boxes to the UK company to see if it

looks feasible.

Floyd --- In Losmandy_users@yahoogroups.com, "Frank Barrett" frankb@...> wrote:

>

> Eric,

>

> > Nice looking frequency spectra. The 34 sec peak is probably causing

> > the minor elongation in your M27 shot (it looks consistent and E-W).

> > It just means you need to guide with ~5 sec exposures, pretty good.

>

> Thanks, I do appreciate your analysis. I agree that the 32 (not 34!)

> second error is the next villain to conquer and is most likely what is

> causing my guider some consternation.

>

> > You know when I guide at 2950mm efl the guider RMS residual is rarely

> > better than 0.6", you have 0.8" unguided...

>

> I am curious how you determined this?

>

> > BTW the PEC graphs you show are the artificial ones that PEMpro

> > created right? The second one looks way too smooth to be raw data.

> > Plus I would advise you to turn off the high frequency modes when

> > genrating the PEC curve, it's trying to model the 32sec term but that

> > term is non-harmonic. You really should just keep the first two

> > harmonics IMHO, they are really the only ones that won't do a random

> > phase jump on you.

>

> Yes, these are the graphs from PEMPro (artificial or not, I believe

> the PE Curve downloaded to the Gemini is based on this, no?).

> Consider me a PEMPro newbie. You are right about the high frequency

> stuff. I did notice the high frequency undulations in the PE Curve

> and speculated that this might be the 32 second error. I will have to

> try this again, perhaps it is why PEC did not give me the results I

> was looking for. But that may have to wait, I am having some issues

> with the camera and it will likely be making a trip back to Santa

> Barbara :(

>

> Frank

> celestialwonders.com

>







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

#39704 Sep 15, 2008

I'll go in for that if you want to do the brain work Floyd. I figure

I was first into Ovision so I'll let s.o. else take the lead on this

one. However, I'll just buy a couple of units to see what's involved

in installation. Not sure I would volunteer any testing. Or put it

another way I'd need someone else to do the testing. I don't think

Harvey would have to software to nail it down to this level. My

participation however may get unit cost down.



regards

Greg N

--- In Losmandy_users@yahoogroups.com, "Floyd Blue" fblue@...> wrote:

>

> It is time for someone to try out the Precision Gear Boxes that we

> discussed earlier.

> I am wondering if our friend in the UK has had any luck investigating

> these?

> I would certainly be willing to pay $30 each plus shipping for them if

> they work. Perhaps it would pay to order a few together to avoid the

> high shipping costs of individual orders. I need to send the specs

> that I found on the Losmandy Gear Boxes to the UK company to see if it

> looks feasible.

> Floyd

> --- In Losmandy_users@yahoogroups.com, "Frank Barrett" frankb@> wrote:

> >

> > Eric,

> >

> > > Nice looking frequency spectra. The 34 sec peak is probably causing

> > > the minor elongation in your M27 shot (it looks consistent and E-W).

> > > It just means you need to guide with ~5 sec exposures, pretty good.

> >

> > Thanks, I do appreciate your analysis. I agree that the 32 (not 34!)

> > second error is the next villain to conquer and is most likely what is

> > causing my guider some consternation.

> >

> > > You know when I guide at 2950mm efl the guider RMS residual is

rarely

> > > better than 0.6", you have 0.8" unguided...

> >

> > I am curious how you determined this?

> >

> > > BTW the PEC graphs you show are the artificial ones that PEMpro

> > > created right? The second one looks way too smooth to be raw data.

> > > Plus I would advise you to turn off the high frequency modes when

> > > genrating the PEC curve, it's trying to model the 32sec term

but that

> > > term is non-harmonic. You really should just keep the first two

> > > harmonics IMHO, they are really the only ones that won't do a random

> > > phase jump on you.

> >

> > Yes, these are the graphs from PEMPro (artificial or not, I believe

> > the PE Curve downloaded to the Gemini is based on this, no?).

> > Consider me a PEMPro newbie. You are right about the high frequency

> > stuff. I did notice the high frequency undulations in the PE Curve

> > and speculated that this might be the 32 second error. I will have to

> > try this again, perhaps it is why PEC did not give me the results I

> > was looking for. But that may have to wait, I am having some issues

> > with the camera and it will likely be making a trip back to Santa

> > Barbara :(

> >

> > Frank

> > celestialwonders.com

> >

>



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

#39705 Sep 15, 2008

I have to correct myself. We had another member who was more deeply

into Ovision than I was, and at an earlier date, and did the beta

testing (in effect). But he was not high profile with his experiments

at the time I got in after NEAF--apparently because he was being

patient with some beta results that weren't too good at first. So

this is like a Leif Erikson/Columbus thing. He made the trip before

me but for whatever reason my venture got more attention. Credit

nonetheless is due, even though I'm forgetting his name...



regards

Greg N

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

>

> I'll go in for that if you want to do the brain work Floyd. I figure

> I was first into Ovision so I'll let s.o. else take the lead on this

> one. However, I'll just buy a couple of units to see what's involved

> in installation. Not sure I would volunteer any testing. Or put it

> another way I'd need someone else to do the testing. I don't think

> Harvey would have to software to nail it down to this level. My

> participation however may get unit cost down.

>

> regards

> Greg N

>



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

#39706 Sep 15, 2008

It was John Moore who went all-in before anyone else. I hope his

current results have been worth it, he did a over a year of unofficial

beta testing. I can only imagine that he must be a very patient

individual.



regards

Greg N

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

>

> I have to correct myself. We had another member who was more deeply

> into Ovision than I was, and at an earlier date, and did the beta

> testing (in effect). But he was not high profile with his experiments



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

#39707 Sep 15, 2008

Hi Frank,

I agree, the $524 for the Ovision only increases the cost of a G-11 by

15% and with the two gear boxes, maybe 16%. This still keeps the G-11

under $4000 with Gemini and a nice transport case. Which is actually a

pretty reasonable cost for a well built mount that can handle 60 lbs

of instruments.

I too do not really need more weight capacity, so it fits my needs

very well.

Floyd --- In Losmandy_users@yahoogroups.com, "Frank Barrett" frankb@...> wrote:

>

> Floyd,

>

> Right on both counts. I just wrote Franck and Gilles and expressed to

> them that my expectations have been far exceeded. Time is, of course,

> the best judge, but I feel strongly that I will look back on this as

> the best $525 I have ever spent. That could be because this solution

> is the perfect fit for my needs. I don't need more weight capacity or

> any other fancy frills...all I've needed is more accurate tracking and

> now, it appears, that enemy has been wounded severely and will

> hopefully be mortally wounded before it is all done. If I can conquer

> the 32 second error the enemy will fall (Assuming PEC will take out

> the remaining 3 arc seconds...I can't believe I just said that, am I

> becoming a PE snob? g>).

>

> Frank

> celestialwonders.com

>

> --- In Losmandy_users@yahoogroups.com, "Floyd Blue" fblue@> wrote:

> >

> > Hi Frank,

> > You must admit that the worm appears to be of excellent quality and

> > certainly meets the manufactures guarantee.

> > Floyd

> > --- In Losmandy_users@yahoogroups.com, "Frank Barrett" frankb@>

wrote:

> > >

> > > Floyd,

> > >

> > > Your recollection is in alignment with mine...our test data were

very

> > > similar, in fact I thought your worst case numbs were slightly

better

> > > than mine. I will eat my shoe if your worm does not perform as well

> > > or better than these results!

> > >

> > > Frank Barrett

> > > celestialwonders.com

> > >

> > > --- In Losmandy_users@yahoogroups.com, "Floyd Blue" fblue@> wrote:

> > > >

> > > > Wow, great results! Your Ovision test report was very similar to

> mine

> > > > as I recall. So I can only hope to see as good of results as you

> > > achieved!

> > > > Floyd

> > > > --- In Losmandy_users@yahoogroups.com, "Frank Barrett" frankb@>

> > wrote:

> > > > >

> > > > > The weather did hold and I was able to retest with the Ovision

> > worm.

> > > > > The adjustments to the mount and the newly charged battery

> made all

> > > > > the difference in the world. The PE is coming in just north of

> > 3 arc

> > > > > seconds. I am still having issues with programming the PEC

on the

> > > > > mount, but I think that may be due to backlevel ASCOM drivers

> on my

> > > > > older laptop (which I use for PEM Pro, long story and I

> digress). I

> > > > > put together a web page showing some of the PEM Pro screen

> shots and

> > > > > for those of you who like to look at images, I posted a

couple of

> > > > > those too.

> > > > >

> > > > > www.celestialwonders.com/equipment/OvisionVsLHPW.html

> > > > >

> > > > > Anyone serious about longer focal length imaging without the

> higher

> > > > > end budget would do well to consider this upgrade.

> > > > >

> > > > > Frank

> > > > > www.celestialwonders.com/equipment/OvisionVsLHPW.html

> > > > >

> > > >

> > >

> >

>







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

#39708 Sep 15, 2008

Hi Greg,

I found this information on the Losmandy gearboxes which should be

enough for the UK manufacturer to tell me whether their box will work.

I will send this to them and ask them whether their box has a similar

tooth arrangement.



G11/Gemini Gearbox



The Gemini/G11 gearbox/motor assembly has an overall reduction ratio

of 25:1. Internal to the gearbox are two gear wheels. The gear

attached to the worm has 75 teeth, the intermediate gear has 10 and 60

teeth, the servo motor has 18 teeth.



The reduction ratios are therefore 75:10 and 60:18, or 7.5:1 and 3.333:1



With a worm period of 240 seconds, that means the intermediate gear is

turning once every 32 seconds, and the motor once every 9.6 seconds

when tracking.



gearbox



Encoder Resolution



The Losmandy motors are fitted with 256 tick/rev encoders, the main

Gemini processor [Gemini has one main processor and two servo

controller processors] uses 'whole' ticks for its calculations giving

the G11 a native resolution of:



arcsec_per_day/(encoder_ticks * gearbox_ratio * worm_ratio)



1,296,000arcsec/(256ticks*25*360) = 0.5626arcsec/tick



The servo controllers actually use the encoders in quadrature mode (to

determine direction of rotation) so they have four times the

resolution = 0.140625 arcsec



Floyd



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

>

> I'll go in for that if you want to do the brain work Floyd. I figure

> I was first into Ovision so I'll let s.o. else take the lead on this

> one. However, I'll just buy a couple of units to see what's involved

> in installation. Not sure I would volunteer any testing. Or put it

> another way I'd need someone else to do the testing. I don't think

> Harvey would have to software to nail it down to this level. My

> participation however may get unit cost down.

>

> regards

> Greg N

>

> --- In Losmandy_users@yahoogroups.com, "Floyd Blue" fblue@> wrote:

> >

> > It is time for someone to try out the Precision Gear Boxes that we

> > discussed earlier.

> > I am wondering if our friend in the UK has had any luck investigating

> > these?

> > I would certainly be willing to pay $30 each plus shipping for them if

> > they work. Perhaps it would pay to order a few together to avoid the

> > high shipping costs of individual orders. I need to send the specs

> > that I found on the Losmandy Gear Boxes to the UK company to see if it

> > looks feasible.

> > Floyd

> > --- In Losmandy_users@yahoogroups.com, "Frank Barrett" frankb@>

wrote:

> > >

> > > Eric,

> > >

> > > > Nice looking frequency spectra. The 34 sec peak is probably

causing

> > > > the minor elongation in your M27 shot (it looks consistent and

E-W).

> > > > It just means you need to guide with ~5 sec exposures, pretty

good.

> > >

> > > Thanks, I do appreciate your analysis. I agree that the 32 (not

34!)

> > > second error is the next villain to conquer and is most likely

what is

> > > causing my guider some consternation.

> > >

> > > > You know when I guide at 2950mm efl the guider RMS residual is

> rarely

> > > > better than 0.6", you have 0.8" unguided...

> > >

> > > I am curious how you determined this?

> > >

> > > > BTW the PEC graphs you show are the artificial ones that PEMpro

> > > > created right? The second one looks way too smooth to be raw data.

> > > > Plus I would advise you to turn off the high frequency modes when

> > > > genrating the PEC curve, it's trying to model the 32sec term

> but that

> > > > term is non-harmonic. You really should just keep the first two

> > > > harmonics IMHO, they are really the only ones that won't do a

random

> > > > phase jump on you.

> > >

> > > Yes, these are the graphs from PEMPro (artificial or not, I believe

> > > the PE Curve downloaded to the Gemini is based on this, no?).

> > > Consider me a PEMPro newbie. You are right about the high frequency

> > > stuff. I did notice the high frequency undulations in the PE Curve

> > > and speculated that this might be the 32 second error. I will

have to

> > > try this again, perhaps it is why PEC did not give me the results I

> > > was looking for. But that may have to wait, I am having some issues

> > > with the camera and it will likely be making a trip back to Santa

> > > Barbara :(

> > >

> > > Frank

> > > celestialwonders.com

> > >

> >

>



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

#39709 Sep 15, 2008

I updated the PE Curves based on Eric's advice to use only the first

two harmonics. The net result is that PE on the Losmandy worm is 5.32

arc seconds and the Ovision is down to a paltry 2.36 arc seconds.

This may sound like I am artificially lowering the score, but it makes

sense if you think about it. The previous curves contained harmonics

that were not the first or second harmonic (i.e. 240 seconds or 120

seconds). These represent noise and should not be used to program the

PEC. It does not mean that my mount tracks at 2.36 arc seconds, but

it does mean that 2.36 arc seconds is due solely to *correctable*

periodic error. The rest (about 2 arc secs) is due to motor noise,

gearbox noise, seeing noise, etc.



Frank

celestialwonders.com

--- In Losmandy_users@yahoogroups.com, "Eric Benson" ebenson@...> wrote:

>

> Frank,

> Nice looking frequency spectra. The 34 sec peak is probably causing

> the minor elongation in your M27 shot (it looks consistent and E-W).

> It just means you need to guide with ~5 sec exposures, pretty good.

>

> You know when I guide at 2950mm efl the guider RMS residual is rarely

> better than 0.6", you have 0.8" unguided...

>

> BTW the PEC graphs you show are the artificial ones that PEMpro

> created right? The second one looks way too smooth to be raw data.

> Plus I would advise you to turn off the high frequency modes when

> genrating the PEC curve, it's trying to model the 32sec term but that

> term is non-harmonic. You really should just keep the first two

> harmonics IMHO, they are really the only ones that won't do a random

> phase jump on you.

>

> Later,

> EB

>

> --- In Losmandy_users@yahoogroups.com, "Frank Barrett" frankb@> wrote:

> >

> > The weather did hold and I was able to retest with the Ovision worm.

> > The adjustments to the mount and the newly charged battery made all

> > the difference in the world. The PE is coming in just north of 3 arc

> > seconds. I am still having issues with programming the PEC on the

> > mount, but I think that may be due to backlevel ASCOM drivers on my

> > older laptop (which I use for PEM Pro, long story and I digress). I

> > put together a web page showing some of the PEM Pro screen shots and

> > for those of you who like to look at images, I posted a couple of

> > those too.

> >

> > www.celestialwonders.com/equipment/OvisionVsLHPW.html

> >

> > Anyone serious about longer focal length imaging without the higher

> > end budget would do well to consider this upgrade.

> >

> > Frank

> > www.celestialwonders.com/equipment/OvisionVsLHPW.html

> >

>







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

#39710 Sep 15, 2008

My hat is off to John. His early testing has no doubt influenced the

excellent results we are seeing now. I may not have been first, but

it does feel good to get in on this early and have the opportunity to

influence others. As you have said, Greg, we are living at a good

time for the G11.



Frank

celestialwonders.com

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

>

> It was John Moore who went all-in before anyone else. I hope his

> current results have been worth it, he did a over a year of unofficial

> beta testing. I can only imagine that he must be a very patient

> individual.

>

> regards

> Greg N

>

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

> >

> > I have to correct myself. We had another member who was more deeply

> > into Ovision than I was, and at an earlier date, and did the beta

> > testing (in effect). But he was not high profile with his experiments

>



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

#39711 Sep 15, 2008

--- In Losmandy_users@yahoogroups.com, "Frank Barrett" frankb@...> wrote: >

> Eric,

>

> > Nice looking frequency spectra. The 34 sec peak is probably causing

> > the minor elongation in your M27 shot (it looks consistent and E-W).

> > It just means you need to guide with ~5 sec exposures, pretty good.

>

> Thanks, I do appreciate your analysis. I agree that the 32 (not 34!)

> second error is the next villain to conquer and is most likely what is

> causing my guider some consternation.



Did I say 34 again!? Freudian slip I guess ;)

>

> > You know when I guide at 2950mm efl the guider RMS residual is rarely

> > better than 0.6", you have 0.8" unguided...

>

> I am curious how you determined this?



Now I'm not exactly sure how PEMpro calculates the RMS value but when

guiding in Maxim the peak error and RMS error are displayed live

(although in pixels so you have to convert to arcsec in your head,

I've been bugging Doug G. about that for a while). I usually ignore

the peak error since it just tells how far off the last cosmic ray

event was from the guide star. However the RMS error is a really good

indicator of guide quality.



For those who are wondering what I'm talking about, Guider RMS is a

measure of how spread out the last x (user selectable) seconds of

guide errors are. The lower the better. There is also a mathematical

relationship (simplified here) between the size of the star in your

final image and the RMS values:

StarFWHM = Sqrt(SeeingFWHM^2 + (2.354*GuideRMS)^2)

you can't do much about seeing disk (except move?!) but you can try to

fix GuideRMS. Also, ideally the RA RMS error = DEC RMS error so that

the stars turn out round. For me, in DEC I usually get 0.1" -> 0.5"

depending on the seeing (SeeingFWHM and GuideRMS are actually coupled

at some level), in RA I occasionally get 0.4", mostly 0.6" and 1" or

more when seeing is really bad or something is wrong mechanically. So

my stars are not round. But if I turn on the AO8 at say >2Hz in good

seeing I get residuals of 0.1" to 0.2" for both, all the time...wish

there were bright guide stars for all my targets ;)



Cheers,

EB



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

#39712 Sep 15, 2008

Hi Frank,

Nice write up you got going there, but I think the captions for Figs.

5 and 6 are swapped.

What was the guider exposure time used in those two pics you show?

Just curious,

EB



--- In Losmandy_users@yahoogroups.com, "Frank Barrett" frankb@...> wrote:

>

> I updated the PE Curves based on Eric's advice to use only the first

> two harmonics. The net result is that PE on the Losmandy worm is 5.32

> arc seconds and the Ovision is down to a paltry 2.36 arc seconds.

> This may sound like I am artificially lowering the score, but it makes

> sense if you think about it. The previous curves contained harmonics

> that were not the first or second harmonic (i.e. 240 seconds or 120

> seconds). These represent noise and should not be used to program the

> PEC. It does not mean that my mount tracks at 2.36 arc seconds, but

> it does mean that 2.36 arc seconds is due solely to *correctable*

> periodic error. The rest (about 2 arc secs) is due to motor noise,

> gearbox noise, seeing noise, etc.

>

> Frank

> celestialwonders.com

>

> --- In Losmandy_users@yahoogroups.com, "Eric Benson" ebenson@> wrote:

> >

> > Frank,

> > Nice looking frequency spectra. The 34 sec peak is probably causing

> > the minor elongation in your M27 shot (it looks consistent and E-W).

> > It just means you need to guide with ~5 sec exposures, pretty good.

> >

> > You know when I guide at 2950mm efl the guider RMS residual is rarely

> > better than 0.6", you have 0.8" unguided...

> >

> > BTW the PEC graphs you show are the artificial ones that PEMpro

> > created right? The second one looks way too smooth to be raw data.

> > Plus I would advise you to turn off the high frequency modes when

> > genrating the PEC curve, it's trying to model the 32sec term but that

> > term is non-harmonic. You really should just keep the first two

> > harmonics IMHO, they are really the only ones that won't do a random

> > phase jump on you.

> >

> > Later,

> > EB

> >

> > --- In Losmandy_users@yahoogroups.com, "Frank Barrett" frankb@>

wrote:

> > >

> > > The weather did hold and I was able to retest with the Ovision

worm.

> > > The adjustments to the mount and the newly charged battery made all

> > > the difference in the world. The PE is coming in just north of

3 arc

> > > seconds. I am still having issues with programming the PEC on the

> > > mount, but I think that may be due to backlevel ASCOM drivers on my

> > > older laptop (which I use for PEM Pro, long story and I digress). I

> > > put together a web page showing some of the PEM Pro screen shots and

> > > for those of you who like to look at images, I posted a couple of

> > > those too.

> > >

> > > www.celestialwonders.com/equipment/OvisionVsLHPW.html

> > >

> > > Anyone serious about longer focal length imaging without the higher

> > > end budget would do well to consider this upgrade.

> > >

> > > Frank

> > > www.celestialwonders.com/equipment/OvisionVsLHPW.html

> > >

> >

>







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

#39713 Sep 15, 2008

Nice write up you got going there, but I think the captions for Figs.

> 5 and 6 are swapped.



Doh! I'll have to fix that!

> What was the guider exposure time used in those two pics you show?

> Just curious,



I am not sure about the M74 shot as that has been awhile, but I would

guess around 6 seconds. The M27 shot was 3 seconds.



Frank

celestialwonders.com



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

#39714 Sep 15, 2008

I believe PemPro RMS value represents the error of the fitted curve

that simply represents how well the computed curve fits the real data.



Regards,



-Paul



--- In Losmandy_users@yahoogroups.com, "Eric Benson" ebenson@...>

wrote: > Now I'm not exactly sure how PEMpro calculates the RMS value



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

#39715 Sep 15, 2008

Are the gear boxes the same for Gemini units as for stepper units?

I'm on steppers, so I won't be coming in if I have a different

build....come to think of it I've heard that the gearing is something

like 150:1 on the steppers...so maybe I'm out?



regards

Greg N

--- In Losmandy_users@yahoogroups.com, "Floyd Blue" fblue@...> wrote:

>

> Hi Greg,

> I found this information on the Losmandy gearboxes which should be

> enough for the UK manufacturer to tell me whether their box will work.

> I will send this to them and ask them whether their box has a similar

> tooth arrangement.

>

> G11/Gemini Gearbox

>

> The Gemini/G11 gearbox/motor assembly has an overall reduction ratio

> of 25:1. Internal to the gearbox are two gear wheels. The gear

> attached to the worm has 75 teeth, the intermediate gear has 10 and 60

> teeth, the servo motor has 18 teeth.

>

> The reduction ratios are therefore 75:10 and 60:18, or 7.5:1 and 3.333:1

>

> With a worm period of 240 seconds, that means the intermediate gear is

> turning once every 32 seconds, and the motor once every 9.6 seconds

> when tracking.

>

> gearbox

>

> Encoder Resolution

>

> The Losmandy motors are fitted with 256 tick/rev encoders, the main

> Gemini processor [Gemini has one main processor and two servo

> controller processors] uses 'whole' ticks for its calculations giving

> the G11 a native resolution of:

>

> arcsec_per_day/(encoder_ticks * gearbox_ratio * worm_ratio)

>

> 1,296,000arcsec/(256ticks*25*360) = 0.5626arcsec/tick

>

> The servo controllers actually use the encoders in quadrature mode (to

> determine direction of rotation) so they have four times the

> resolution = 0.140625 arcsec

>

> Floyd

>

>

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

> >

> > I'll go in for that if you want to do the brain work Floyd. I figure

> > I was first into Ovision so I'll let s.o. else take the lead on this

> > one. However, I'll just buy a couple of units to see what's involved

> > in installation. Not sure I would volunteer any testing. Or put it

> > another way I'd need someone else to do the testing. I don't think

> > Harvey would have to software to nail it down to this level. My

> > participation however may get unit cost down.

> >

> > regards

> > Greg N

> >

> > --- In Losmandy_users@yahoogroups.com, "Floyd Blue" fblue@> wrote:

> > >

> > > It is time for someone to try out the Precision Gear Boxes that we

> > > discussed earlier.

> > > I am wondering if our friend in the UK has had any luck

investigating

> > > these?

> > > I would certainly be willing to pay $30 each plus shipping for

them if

> > > they work. Perhaps it would pay to order a few together to avoid the

> > > high shipping costs of individual orders. I need to send the specs

> > > that I found on the Losmandy Gear Boxes to the UK company to see

if it

> > > looks feasible.

> > > Floyd

> > > --- In Losmandy_users@yahoogroups.com, "Frank Barrett" frankb@>

> wrote:

> > > >

> > > > Eric,

> > > >

> > > > > Nice looking frequency spectra. The 34 sec peak is probably

> causing

> > > > > the minor elongation in your M27 shot (it looks consistent and

> E-W).

> > > > > It just means you need to guide with ~5 sec exposures, pretty

> good.

> > > >

> > > > Thanks, I do appreciate your analysis. I agree that the 32 (not

> 34!)

> > > > second error is the next villain to conquer and is most likely

> what is

> > > > causing my guider some consternation.

> > > >

> > > > > You know when I guide at 2950mm efl the guider RMS residual is

> > rarely

> > > > > better than 0.6", you have 0.8" unguided...

> > > >

> > > > I am curious how you determined this?

> > > >

> > > > > BTW the PEC graphs you show are the artificial ones that PEMpro

> > > > > created right? The second one looks way too smooth to be raw

data.

> > > > > Plus I would advise you to turn off the high frequency modes

when

> > > > > genrating the PEC curve, it's trying to model the 32sec term

> > but that

> > > > > term is non-harmonic. You really should just keep the first two

> > > > > harmonics IMHO, they are really the only ones that won't do a

> random

> > > > > phase jump on you.

> > > >

> > > > Yes, these are the graphs from PEMPro (artificial or not, I

believe

> > > > the PE Curve downloaded to the Gemini is based on this, no?).

> > > > Consider me a PEMPro newbie. You are right about the high

frequency

> > > > stuff. I did notice the high frequency undulations in the PE

Curve

> > > > and speculated that this might be the 32 second error. I will

> have to

> > > > try this again, perhaps it is why PEC did not give me the

results I

> > > > was looking for. But that may have to wait, I am having some

issues

> > > > with the camera and it will likely be making a trip back to Santa

> > > > Barbara :(

> > > >

> > > > Frank

> > > > celestialwonders.com

> > > >

> > >

> >

>







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

#39716 Sep 15, 2008

Well if I knew what you were talking about I'm sure I'd like to adjust

my numbers down too! Greg N

--- In Losmandy_users@yahoogroups.com, "Frank Barrett" frankb@...> wrote:

>

> I updated the PE Curves based on Eric's advice to use only the first

> two harmonics. The net result is that PE on the Losmandy worm is 5.32

> arc seconds and the Ovision is down to a paltry 2.36 arc seconds.

> This may sound like I am artificially lowering the score, but it makes

> sense if you think about it. The previous curves contained harmonics

> that were not the first or second harmonic (i.e. 240 seconds or 120

> seconds). These represent noise and should not be used to program the

> PEC. It does not mean that my mount tracks at 2.36 arc seconds, but

> it does mean that 2.36 arc seconds is due solely to *correctable*

> periodic error. The rest (about 2 arc secs) is due to motor noise,

> gearbox noise, seeing noise, etc.

>

> Frank

> celestialwonders.com

>

> --- In Losmandy_users@yahoogroups.com, "Eric Benson" ebenson@> wrote:

> >

> > Frank,

> > Nice looking frequency spectra. The 34 sec peak is probably causing

> > the minor elongation in your M27 shot (it looks consistent and E-W).

> > It just means you need to guide with ~5 sec exposures, pretty good.

> >

> > You know when I guide at 2950mm efl the guider RMS residual is rarely

> > better than 0.6", you have 0.8" unguided...

> >

> > BTW the PEC graphs you show are the artificial ones that PEMpro

> > created right? The second one looks way too smooth to be raw data.

> > Plus I would advise you to turn off the high frequency modes when

> > genrating the PEC curve, it's trying to model the 32sec term but that

> > term is non-harmonic. You really should just keep the first two

> > harmonics IMHO, they are really the only ones that won't do a random

> > phase jump on you.

> >

> > Later,

> > EB

> >

> > --- In Losmandy_users@yahoogroups.com, "Frank Barrett" frankb@>

wrote:

> > >

> > > The weather did hold and I was able to retest with the Ovision

worm.

> > > The adjustments to the mount and the newly charged battery made all

> > > the difference in the world. The PE is coming in just north of

3 arc

> > > seconds. I am still having issues with programming the PEC on the

> > > mount, but I think that may be due to backlevel ASCOM drivers on my

> > > older laptop (which I use for PEM Pro, long story and I digress). I

> > > put together a web page showing some of the PEM Pro screen shots and

> > > for those of you who like to look at images, I posted a couple of

> > > those too.

> > >

> > > www.celestialwonders.com/equipment/OvisionVsLHPW.html

> > >

> > > Anyone serious about longer focal length imaging without the higher

> > > end budget would do well to consider this upgrade.

> > >

> > > Frank

> > > www.celestialwonders.com/equipment/OvisionVsLHPW.html

> > >

> >

>



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

#39717 Sep 15, 2008

Greg,



No. The stepper uses a 150:1 and the Gemini servo are either the 25 or 50:1. They also have

different shapes.



Don

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

From: "gnowellsct" tim71pos@...>

To: Losmandy_users@yahoogroups.com>

Sent: Monday, September 15, 2008 8:58 PM

Subject: [Losmandy_users] Re: Ovision results - confirmed (stepper vs Gemini gearboxes?)





> Are the gear boxes the same for Gemini units as for stepper units?

> I'm on steppers, so I won't be coming in if I have a different

> build....come to think of it I've heard that the gearing is something

> like 150:1 on the steppers...so maybe I'm out?

>

> regards

> Greg N



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

#39720 Sep 15, 2008

Hi Greg,

I do not know for sure about that.

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

>

> Are the gear boxes the same for Gemini units as for stepper units?

> I'm on steppers, so I won't be coming in if I have a different

> build....come to think of it I've heard that the gearing is something

> like 150:1 on the steppers...so maybe I'm out?

>

> regards

> Greg N

>

> --- In Losmandy_users@yahoogroups.com, "Floyd Blue" fblue@> wrote:

> >

> > Hi Greg,

> > I found this information on the Losmandy gearboxes which should be

> > enough for the UK manufacturer to tell me whether their box will work.

> > I will send this to them and ask them whether their box has a similar

> > tooth arrangement.

> >

> > G11/Gemini Gearbox

> >

> > The Gemini/G11 gearbox/motor assembly has an overall reduction ratio

> > of 25:1. Internal to the gearbox are two gear wheels. The gear

> > attached to the worm has 75 teeth, the intermediate gear has 10 and 60

> > teeth, the servo motor has 18 teeth.

> >

> > The reduction ratios are therefore 75:10 and 60:18, or 7.5:1 and

3.333:1

> >

> > With a worm period of 240 seconds, that means the intermediate gear is

> > turning once every 32 seconds, and the motor once every 9.6 seconds

> > when tracking.

> >

> > gearbox

> >

> > Encoder Resolution

> >

> > The Losmandy motors are fitted with 256 tick/rev encoders, the main

> > Gemini processor [Gemini has one main processor and two servo

> > controller processors] uses 'whole' ticks for its calculations giving

> > the G11 a native resolution of:

> >

> > arcsec_per_day/(encoder_ticks * gearbox_ratio * worm_ratio)

> >

> > 1,296,000arcsec/(256ticks*25*360) = 0.5626arcsec/tick

> >

> > The servo controllers actually use the encoders in quadrature mode (to

> > determine direction of rotation) so they have four times the

> > resolution = 0.140625 arcsec

> >

> > Floyd

> >

> >

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

> > >

> > > I'll go in for that if you want to do the brain work Floyd. I

figure

> > > I was first into Ovision so I'll let s.o. else take the lead on this

> > > one. However, I'll just buy a couple of units to see what's

involved

> > > in installation. Not sure I would volunteer any testing. Or put it

> > > another way I'd need someone else to do the testing. I don't think

> > > Harvey would have to software to nail it down to this level. My

> > > participation however may get unit cost down.

> > >

> > > regards

> > > Greg N

> > >

> > > --- In Losmandy_users@yahoogroups.com, "Floyd Blue" fblue@> wrote:

> > > >

> > > > It is time for someone to try out the Precision Gear Boxes that we

> > > > discussed earlier.

> > > > I am wondering if our friend in the UK has had any luck

> investigating

> > > > these?

> > > > I would certainly be willing to pay $30 each plus shipping for

> them if

> > > > they work. Perhaps it would pay to order a few together to

avoid the

> > > > high shipping costs of individual orders. I need to send the specs

> > > > that I found on the Losmandy Gear Boxes to the UK company to see

> if it

> > > > looks feasible.

> > > > Floyd

> > > > --- In Losmandy_users@yahoogroups.com, "Frank Barrett" frankb@>

> > wrote:

> > > > >

> > > > > Eric,

> > > > >

> > > > > > Nice looking frequency spectra. The 34 sec peak is probably

> > causing

> > > > > > the minor elongation in your M27 shot (it looks consistent and

> > E-W).

> > > > > > It just means you need to guide with ~5 sec exposures, pretty

> > good.

> > > > >

> > > > > Thanks, I do appreciate your analysis. I agree that the 32 (not

> > 34!)

> > > > > second error is the next villain to conquer and is most likely

> > what is

> > > > > causing my guider some consternation.

> > > > >

> > > > > > You know when I guide at 2950mm efl the guider RMS residual is

> > > rarely

> > > > > > better than 0.6", you have 0.8" unguided...

> > > > >

> > > > > I am curious how you determined this?

> > > > >

> > > > > > BTW the PEC graphs you show are the artificial ones that

PEMpro

> > > > > > created right? The second one looks way too smooth to be raw

> data.

> > > > > > Plus I would advise you to turn off the high frequency modes

> when

> > > > > > genrating the PEC curve, it's trying to model the 32sec term

> > > but that

> > > > > > term is non-harmonic. You really should just keep the

first two

> > > > > > harmonics IMHO, they are really the only ones that won't do a

> > random

> > > > > > phase jump on you.

> > > > >

> > > > > Yes, these are the graphs from PEMPro (artificial or not, I

> believe

> > > > > the PE Curve downloaded to the Gemini is based on this, no?).

> > > > > Consider me a PEMPro newbie. You are right about the high

> frequency

> > > > > stuff. I did notice the high frequency undulations in the PE

> Curve

> > > > > and speculated that this might be the 32 second error. I will

> > have to

> > > > > try this again, perhaps it is why PEC did not give me the

> results I

> > > > > was looking for. But that may have to wait, I am having some

> issues

> > > > > with the camera and it will likely be making a trip back to

Santa

> > > > > Barbara :(

> > > > >

> > > > > Frank

> > > > > celestialwonders.com

> > > > >

> > > >

> > >

> >

>







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

#39739 Sep 16, 2008

Thanks for that Don. I knew there was an alarm bell going off dimly

in my brain. Floyd, looks like I'm out. Greg N

--- In Losmandy_users@yahoogroups.com, "Don D'Egidio" djd521@...> wrote:

>

> Greg,

>

> No. The stepper uses a 150:1 and the Gemini servo are either the 25

or 50:1. They also have

> different shapes.

>

> Don

>



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

#39741 Sep 16, 2008

Now I'm not exactly sure how PEMpro calculates the RMS value but when

> guiding in Maxim the peak error and RMS error are displayed live

> (although in pixels so you have to convert to arcsec in your head,

> I've been bugging Doug G. about that for a while). I usually ignore

> the peak error since it just tells how far off the last cosmic ray

> event was from the guide star. However the RMS error is a really good

> indicator of guide quality.



I think Paul is right, the RMS value in PEMPro is relative to the

curve fit and not indicative of potential guiding accuracy. I use

CCDSoft which is even worse in how it reports guide corrections. Not

only are the values in pixels and not arc seconds, but the X and Y

values are not rotated to the RA and Dec axes. RMS values are not

reported at all. However, all the data, including the position angle

is available in the log file. I whipped up a spreadsheet to calculate

the RMS values, post analysis style. It rotates the axes, converts

pixels to arcsecs and calculates the RMS values. The Ovision run

where I captured M27 had an RA RMS of 1.2 arc secs and the Dec was 0.8

arc seconds (my seeing is usually pretty lousy). That seems

consistent with the star shapes I am getting. Actually, I had done

this analysis before your post and have thought about writing a script

that would query CCDSoft's guiding errors realtime and report the RMS

values for RA and Dec. Long-post-short, I agree that guider RMS

expressed in arc seconds and reported realtime is an invaluable tool

to the imager both in terms of guide quality but also to put a

yardstick on seeing. >

> For those who are wondering what I'm talking about, Guider RMS is a

> measure of how spread out the last x (user selectable) seconds of

> guide errors are. The lower the better. There is also a mathematical

> relationship (simplified here) between the size of the star in your

> final image and the RMS values:

> StarFWHM = Sqrt(SeeingFWHM^2 + (2.354*GuideRMS)^2)



An interesting formula. I won't ask for the derivation g> but it

does make intuitive sense that the star size would be dependent on

both seeing and guiding. When guider RMS is near zero the seeing will

dictate star size. Well, not completely, the optical quality and

collimation would also play a factor as well.



Frank

celestialwonders.com



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

#39755 Sep 16, 2008

Not a problem Greg! Hey, if I find that the gearbox will work, I will

just order two of them and give them a try. If they work, fine. If

not, no big loss either.

I am getting together information to send to the UK and see what they

have to say.

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

>

> Thanks for that Don. I knew there was an alarm bell going off dimly

> in my brain. Floyd, looks like I'm out. Greg N

>

> --- In Losmandy_users@yahoogroups.com, "Don D'Egidio" djd521@> wrote:

> >

> > Greg,

> >

> > No. The stepper uses a 150:1 and the Gemini servo are either the 25

> or 50:1. They also have

> > different shapes.

> >

> > Don

> >

>



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