PEC


Vince Salfranc
 

I am trying to program the PEM on my AP900 without any success.

Could someone be kind enough to help me.

1.Do I need to point the mount to a particular part of the sky before doing the data capture to create the correction curve. 

2.which option should I use to create the curve.

3.I have tried to create a curve and sent it to the mount but the guiding is no better even worse.

4. I have inverted the curve but still no improvement.

5.I can get a 5 minute exposure with no trailing when I an not autoguiding.

Thank you for your help.

Vince


Roland Christen
 

Are you using PEMPro? If so, point the mount to somewhere near the meridian and the celestial equator (also known as Dec zero). Once you have the data, analyze the curve. The program should tell you the amount of PE. Then create the PE curve and simply load it to the mount. Do not invert the curve.
 
To get a good curve I would let the mount gather data for about 30 - 40 minutes to get 5 to 6 cycles. PEMPro will average them, smooth them, and then you can load it to the mount servo. I would not do any more than that for your application.
 
Rolando
 
 

-----Original Message-----
From: salfranc@... [ap-gto]
To: ap-gto
Sent: Fri, Aug 19, 2016 6:53 am
Subject: [ap-gto] PEC



I am trying to program the PEM on my AP900 without any success.
Could someone be kind enough to help me.
1.Do I need to point the mount to a particular part of the sky before doing the data capture to create the correction curve. 
2.which option should I use to create the curve.
3.I have tried to create a curve and sent it to the mount but the guiding is no better even worse.
4. I have inverted the curve but still no improvement.
5.I can get a 5 minute exposure with no trailing when I an not autoguiding.
Thank you for your help.
Vince



Christopher Erickson
 

Did you run the calibration wizard to find out your true image scale before acquiring data?
 
My true image scale was a full 5% different than the mathematically-calculated value for my OTA+flattener+camera.
 
 
Christopher Erickson
Consulting Engineer
Summit Kinetics
Waikoloa, HI 96738
www.summitkinetics.com
 



From: ap-gto@... [mailto:ap-gto@...]
Sent: Friday, August 19, 2016 1:53 AM
To: ap-gto@...
Subject: [ap-gto] PEC

I am trying to program the PEM on my AP900 without any success.

Could someone be kind enough to help me.

1.Do I need to point the mount to a particular part of the sky before doing the data capture to create the correction curve. 

2.which option should I use to create the curve.

3.I have tried to create a curve and sent it to the mount but the guiding is no better even worse.

4. I have inverted the curve but still no improvement.

5.I can get a 5 minute exposure with no trailing when I an not autoguiding.

Thank you for your help.

Vince


Christopher Erickson
 

Here is what I do to generate a new PEMPro PEC curve for an AP mount. It is
possible that the "perfectly-correct" way is a bit different but this has
worked for me:


1. Download the latest beta version of PEMPro V3 Beta.

2. Under PEC/Setup tab - "Configure Scopes/Mounts".

3. Now configure "Connect Camera".

4. Do a reasonably-good polar alignment. No need to get too fanatical or
spend too much time trying to do a drift alignment or using the Polar Align
Wizard.

5. When the mount and camera are configured correctly and working, run the
"Wizards/Calibration Wizard" This will allow you to get the true image
scale of your optical setup and camera. It is rarely exactly what the
theoretical calculation says it will be so a real-world measurement is
critical to getting a good, valid PEC curve. My AP 130EDF-GT refractor with
flattener and SBIG STF-8300M camera has a theoretical image scale of 1.32
arcseconds per pixel. The Calibration Wizard showed that it was really
1.285. Probably the flattener was primarily responsible for that
difference. At any rate that is enough difference to have created a poor
PEC curve.

6. Next step is to "Acquire Data". Make sure PEC is turned off at this
step. I try to pick a clear, stable night. However less-stable nights are
useable if you do a lot of "worm turns" (I do about an hour's-worth per run)
and let the software automatically integrate them.

7. When done with "Acquire Data", the software will step you through to
"Program Mount". On very turbulent nights I might spend some time
"smoothing" the data under the "AP Raw PE" tab with a scale value of 1.25 or
so. Running more worm turns would probably be a better approach, but
sometimes I am a bit lazy and impatient.

8. Done!

Now you can run another curve with PEC turned on and see how it compares.

There is a lot of advanced stuff you can do and get real mathematical but
these basics have worked sufficiently for me.

I hope this helps.


Christopher Erickson
Consulting Engineer
Summit Kinetics
Waikoloa, HI 96738
www.summitkinetics.com




________________________________

From: Christopher Erickson [mailto:christopher.k.erickson@gmail.com]
Sent: Friday, August 19, 2016 7:17 AM
To: 'ap-gto@yahoogroups.com'
Subject: RE: [ap-gto] PEC


Did you run the calibration wizard to find out your true image scale before
acquiring data?

My true image scale was a full 5% different than the
mathematically-calculated value for my OTA+flattener+camera.


Christopher Erickson
Consulting Engineer
Summit Kinetics
Waikoloa, HI 96738
www.summitkinetics.com



________________________________

From: ap-gto@yahoogroups.com [mailto:ap-gto@yahoogroups.com]
Sent: Friday, August 19, 2016 1:53 AM
To: ap-gto@yahoogroups.com
Subject: [ap-gto] PEC





I am trying to program the PEM on my AP900 without any success.

Could someone be kind enough to help me.

1.Do I need to point the mount to a particular part of the sky before doing
the data capture to create the correction curve.

2.which option should I use to create the curve.

3.I have tried to create a curve and sent it to the mount but the guiding is
no better even worse.

4. I have inverted the curve but still no improvement.

5.I can get a 5 minute exposure with no trailing when I an not autoguiding.

Thank you for your help.

Vince


Vince Salfranc
 

Thank you for all the advise. I seem to have done all of this and somehow there is no improvement.
I am using Pempro as described here, created the curse and then send it to the mount. Then I done a new acquire data with the pem on and there is no improvement.
I have also tried to reverse the curve but still no luck.
Thank you for your help.
Vince


Ray Gralak
 

Hi Vince,

Can you zip all the files from your last session and email the zip file to me (groups3 AT gralak dot com), or post them in the files section?

Thanks,

-Ray Gralak
Author of APCC (Astro-Physics Command Center): http://www.astro-physics.com/index.htm?products/accessories/software/apcc/apcc
Author of PEMPro: http://www.ccdware.com
Author of Astro-Physics V2 ASCOM Driver: http://www.gralak.com/apdriver
Author of PulseGuide: http://www.pulseguide.com
Author of Sigma: http://www.gralak.com/sigma

-----Original Message-----
From: ap-gto@yahoogroups.com [mailto:ap-gto@yahoogroups.com]
Sent: Saturday, August 20, 2016 2:57 AM
To: ap-gto@yahoogroups.com
Subject: [ap-gto] Re: PEC



Thank you for all the advise. I seem to have done all of this and somehow there is no
improvement.
I am using Pempro as described here, created the curse and then send it to the
mount. Then I done a new acquire data with the pem on and there is no
improvement.
I have also tried to reverse the curve but still no luck.
Thank you for your help.
Vince



Vince Salfranc
 

Hi Ray,
Many thanks for your help. Files are on their way.
Vince


Ray Gralak
 

Hi Vince,

Thanks! I got your files.

I think I see at least one problem: image scale is set to "1" (exactly), and the camera angle is "0.0000". Those are the defaults, which indicates to me that you did not run the Calibration Wizard first. That will establish camera angle and image scale, which are crucial to getting a good result.

Please take a look at the Astro-Physics GTOCP3 section in the help file. This section applies to the GTOCP4 as well. An easy way to get to the help file is by pressing the F1 key when PEMPro is running. Or, you can find the same information here online:

http://www.siriusimaging.com/Help/PEMProV2new/index.html?astrophysicsgtocp3.html

-Ray Gralak
Author of APCC (Astro-Physics Command Center): http://www.astro-physics.com/index.htm?products/accessories/software/apcc/apcc
Author of PEMPro: http://www.ccdware.com
Author of Astro-Physics V2 ASCOM Driver: http://www.gralak.com/apdriver
Author of PulseGuide: http://www.pulseguide.com
Author of Sigma: http://www.gralak.com/sigma

-----Original Message-----
From: ap-gto@yahoogroups.com [mailto:ap-gto@yahoogroups.com]
Sent: Saturday, August 20, 2016 6:34 AM
To: ap-gto@yahoogroups.com
Subject: RE: [ap-gto] Re: PEC



Hi Ray,
Many thanks for your help. Files are on their way.
Vince



Larry Phillips
 

Ray, excuse me for butting into this conversation.  But the reference you made about the Calibration Wizard says you only need to do this once.  Is this also true if I remove the telescope/camera and later replace it on the mount (a refractor) and the camera angle is slightly off from its previous position?

Larry


Ray Gralak
 

Hi Larry,

I think I meant that considering nothing changes (like maybe in a permanent setup). More accurately, you will usually need to do the calibration wizard once per night. However, if you change equipment or camera orientation then you will need to calibrate again. If you do a pier flip, you don't necessarily need to calibrate, but you may have to invert the PEC curve.

-Ray Gralak
Author of APCC (Astro-Physics Command Center): http://www.astro-physics.com/index.htm?products/accessories/software/apcc/apcc
Author of PEMPro: http://www.ccdware.com
Author of Astro-Physics V2 ASCOM Driver: http://www.gralak.com/apdriver
Author of PulseGuide: http://www.pulseguide.com
Author of Sigma: http://www.gralak.com/sigma

-----Original Message-----
From: ap-gto@yahoogroups.com [mailto:ap-gto@yahoogroups.com]
Sent: Saturday, August 20, 2016 8:08 AM
To: ap-gto@yahoogroups.com
Subject: RE: [ap-gto] Re: PEC



Ray, excuse me for butting into this conversation. But the reference you made about
the Calibration Wizard says you only need to do this once. Is this also true if I
remove the telescope/camera and later replace it on the mount (a refractor) and the
camera angle is slightly off from its previous position?

Larry


Joe Zeglinski
 

Ray,
 
    To your point about calibration after a pier flip. I was thinking it would be better to run calibration, but also just SKIP ahead to the step that the user selects the “hockey stick” pattern, and changes it “diagonally” to the previous pier side’s calibration run, selected one.
 
    That way, the camera is not touched or adjusted, which would change the camera angle from the original pier side calibration. I have found the scale changes “somewhat”, if I go through ALL the calibration steps,  on the flip side. It may account for my getting  different PEC curve coefficients on alternate pier sides.
 
Joe


Roland Christen
 

"but you may have to invert the PEC curve."
 
You NEVER have to invert the PEC curve. Calibration is not the same as producing a PE curve and uploading it to your mount servo. Let's not confuse the two. Once you have done a PE run and uploaded a PE curve to the mount, you should not have to do this again for a couple of years. Calibration of your camera for autoguiding is a whole other issue. There is no reason to do a PE curve willy nilly every time you set up. That is just bonkers.
 
Another observation: after doing a PE run, you can retrieve the curve that was loaded into your mount, and that will tell you whether or not you have done the run successfully. It will look just like the curve that you generated and uploaded.
 
If, after turning PE on, you still get drift in RA, then you probably are not properly polar aligned. However, even with perfect polar alignment, the RA axis will still drift due to atmospheric refraction. The only place where the exact sidereal rate produces no drift is at the zenith. Everywhere else the stars will drift slowly or rapidly depending on how far from the horizon you are pointing. The only way to eliminate RA drift (and Dec drift) is to model the sky and allow the model to modify the tracking rates.
 
Is it possible to determine if the RA drift is due to PE or to drift? Yes, but this requires a bit of old fashioned experimentation. Drift is constant, PE is cyclical. You can see the cyclical motion of PE by offsetting azimuth axis about 5 to 10 degrees and recording star drift with your CCD camera for about 13 minutes. You will get two worm cycles in your image, and you can then measure the amount of periodic error by looking at the cyclical trail of any star in your image. Measuring the number of pixel variation of the cycles will give you the amount of PE. If the star streaks are basically straight, then there is little or no periodic error. Do this with PEM on and PEM off to see the improvement.
 
Rolando
 
 

-----Original Message-----
From: 'Ray Gralak (Groups)' groups3@... [ap-gto]
To: ap-gto
Sent: Sat, Aug 20, 2016 10:26 am
Subject: RE: [ap-gto] Re: PEC

Hi Larry,

I think I meant that considering nothing changes (like maybe in a permanent setup). More accurately, you will usually need to do the calibration wizard once per night. However, if you change equipment or camera orientation then you will need to calibrate again. If you do a pier flip, you don't necessarily need to calibrate, but you may have to invert the PEC curve.

-Ray Gralak
Author of APCC (Astro-Physics Command Center): http://www.astro-physics.com/index.htm?products/accessories/software/apcc/apcc
Author of PEMPro: http://www.ccdware.com
Author of Astro-Physics V2 ASCOM Driver: http://www.gralak.com/apdriver
Author of PulseGuide: http://www.pulseguide.com
Author of Sigma: http://www.gralak.com/sigma


> -----Original Message-----
> From: ap-gto@... [mailto:ap-gto@...]
> Sent: Saturday, August 20, 2016 8:08 AM
> To: ap-gto@...
> Subject: RE: [ap-gto] Re: PEC
>
>
>
> Ray, excuse me for butting into this conversation. But the reference you made about
> the Calibration Wizard says you only need to do this once. Is this also true if I
> remove the telescope/camera and later replace it on the mount (a refractor) and the
> camera angle is slightly off from its previous position?
>
> Larry
>
>



------------------------------------
Posted by: "Ray Gralak \(Groups\)" <groups3@...>
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Ray Gralak
 

Hi Roland,

"but you may have to invert the PEC curve."

You NEVER have to invert the PEC curve.
After a pier flip, the camera will effectively be rotated 180 degrees. What was West on an image is now East, and vice versa.

So, if the user ran PEMPro's Calibration Wizard on one side of the pier, and then did a pier flip, PEMPro won't know that the camera was effectively rotated 180 degrees. To compensate for the camera rotation the user can invert the PEC curve before uploading to the mount, or rerun PEMPro's Calibration Wizard.

-Ray Gralak
Author of APCC (Astro-Physics Command Center): http://www.astro-physics.com/index.htm?products/accessories/software/apcc/apcc
Author of PEMPro: http://www.ccdware.com
Author of Astro-Physics V2 ASCOM Driver: http://www.gralak.com/apdriver
Author of PulseGuide: http://www.pulseguide.com
Author of Sigma: http://www.gralak.com/sigma


-----Original Message-----
From: ap-gto@yahoogroups.com [mailto:ap-gto@yahoogroups.com]
Sent: Saturday, August 20, 2016 9:56 AM
To: ap-gto@yahoogroups.com
Subject: Re: [ap-gto] Re: PEC



"but you may have to invert the PEC curve."

You NEVER have to invert the PEC curve. Calibration is not the same as producing a
PE curve and uploading it to your mount servo. Let's not confuse the two. Once you
have done a PE run and uploaded a PE curve to the mount, you should not have to
do this again for a couple of years. Calibration of your camera for autoguiding is a
whole other issue. There is no reason to do a PE curve willy nilly every time you set
up. That is just bonkers.

Another observation: after doing a PE run, you can retrieve the curve that was loaded
into your mount, and that will tell you whether or not you have done the run
successfully. It will look just like the curve that you generated and uploaded.

If, after turning PE on, you still get drift in RA, then you probably are not properly
polar aligned. However, even with perfect polar alignment, the RA axis will still drift
due to atmospheric refraction. The only place where the exact sidereal rate produces
no drift is at the zenith. Everywhere else the stars will drift slowly or rapidly depending
on how far from the horizon you are pointing. The only way to eliminate RA drift (and
Dec drift) is to model the sky and allow the model to modify the tracking rates.

Is it possible to determine if the RA drift is due to PE or to drift? Yes, but this requires
a bit of old fashioned experimentation. Drift is constant, PE is cyclical. You can see
the cyclical motion of PE by offsetting azimuth axis about 5 to 10 degrees and
recording star drift with your CCD camera for about 13 minutes. You will get two
worm cycles in your image, and you can then measure the amount of periodic error
by looking at the cyclical trail of any star in your image. Measuring the number of
pixel variation of the cycles will give you the amount of PE. If the star streaks are
basically straight, then there is little or no periodic error. Do this with PEM on and
PEM off to see the improvement.

Rolando


-----Original Message-----
From: 'Ray Gralak (Groups)' groups3@gralak.com [ap-gto] <ap-
gto@yahoogroups.com>
To: ap-gto <ap-gto@yahoogroups.com>
Sent: Sat, Aug 20, 2016 10:26 am
Subject: RE: [ap-gto] Re: PEC

Hi Larry,

I think I meant that considering nothing changes (like maybe in a permanent setup).
More accurately, you will usually need to do the calibration wizard once per night.
However, if you change equipment or camera orientation then you will need to
calibrate again. If you do a pier flip, you don't necessarily need to calibrate, but you
may have to invert the PEC curve.

-Ray Gralak
Author of APCC (Astro-Physics Command Center): http://www.astro-
physics.com/index.htm?products/accessories/software/apcc/apcc
Author of PEMPro: http://www.ccdware.com
Author of Astro-Physics V2 ASCOM Driver: http://www.gralak.com/apdriver
Author of PulseGuide: http://www.pulseguide.com
Author of Sigma: http://www.gralak.com/sigma


-----Original Message-----
From: ap-gto@yahoogroups.com [mailto:ap-gto@yahoogroups.com <mailto:ap-
gto@yahoogroups.com?> ]
Sent: Saturday, August 20, 2016 8:08 AM
To: ap-gto@yahoogroups.com
Subject: RE: [ap-gto] Re: PEC



Ray, excuse me for butting into this conversation. But the reference you made
about
the Calibration Wizard says you only need to do this once. Is this also true if I
remove the telescope/camera and later replace it on the mount (a refractor) and the
camera angle is slightly off from its previous position?

Larry



------------------------------------
Posted by: "Ray Gralak &#92;(Groups&#92;)" <groups3@gralak.com>
------------------------------------

To UNSUBSCRIBE, or for general information on the ap-gto list
see http://groups.yahoo.com/group/ap-gto
------------------------------------

Yahoo Groups Links






Ray Gralak
 

Hi Joe,

I have found the scale changes “somewhat”, if I go through ALL the
calibration steps, on the flip side.
One possible reason for image scale changes could be "settling" of equipment after the pier flip.

Also, the accuracy of the calculated image scale depends on how accurately you click the start and ends of star trails, so there can be some variation. You can try zooming in first to click an endpoint. But, you don't want to click the very last pixels of a trail. The trail has a width and so at each end you want to pick a point 1/2 the trail width from the very ends of the trail.

It may account for my getting different PEC curve coefficients on
alternate pier sides.
I have seen this to in my 1200, but I don't think it has anything to do with image scale. It may have something to so with how the worm rides on the worm wheel on each side of the pier when there is a weight imbalance.

-Ray Gralak
Author of APCC (Astro-Physics Command Center): http://www.astro-physics.com/index.htm?products/accessories/software/apcc/apcc
Author of PEMPro: http://www.ccdware.com
Author of Astro-Physics V2 ASCOM Driver: http://www.gralak.com/apdriver
Author of PulseGuide: http://www.pulseguide.com
Author of Sigma: http://www.gralak.com/sigma


-----Original Message-----
From: ap-gto@yahoogroups.com [mailto:ap-gto@yahoogroups.com]
Sent: Saturday, August 20, 2016 9:05 AM
To: ap-gto@yahoogroups.com
Subject: Re: [ap-gto] Re: PEC



Ray,

To your point about calibration after a pier flip. I was thinking it would be better to
run calibration, but also just SKIP ahead to the step that the user selects the “hockey
stick” pattern, and changes it “diagonally” to the previous pier side’s calibration run,
selected one.

That way, the camera is not touched or adjusted, which would change the camera
angle from the original pier side calibration. I have found the scale changes
“somewhat”, if I go through ALL the calibration steps, on the flip side. It may account
for my getting different PEC curve coefficients on alternate pier sides.

Joe


Roland Christen
 

Ok, I see what you are saying. However, one should not be flipping the mount during a PEMPro run.
 
Roland
 
 

-----Original Message-----
From: 'Ray Gralak (Groups)' groups3@... [ap-gto]
To: ap-gto
Sent: Sat, Aug 20, 2016 12:19 pm
Subject: RE: [ap-gto] Re: PEC

Hi Roland,

> "but you may have to invert the PEC curve."
>
> You NEVER have to invert the PEC curve.

After a pier flip, the camera will effectively be rotated 180 degrees. What was West on an image is now East, and vice versa.

So, if the user ran PEMPro's Calibration Wizard on one side of the pier, and then did a pier flip, PEMPro won't know that the camera was effectively rotated 180 degrees. To compensate for the camera rotation the user can invert the PEC curve before uploading to the mount, or rerun PEMPro's Calibration Wizard.

-Ray Gralak
Author of APCC (Astro-Physics Command Center): http://www.astro-physics.com/index.htm?products/accessories/software/apcc/apcc
Author of PEMPro: http://www.ccdware.com
Author of Astro-Physics V2 ASCOM Driver: http://www.gralak.com/apdriver
Author of PulseGuide: http://www.pulseguide.com
Author of Sigma: http://www.gralak.com/sigma


> -----Original Message-----
> From: ap-gto@... [mailto:ap-gto@...]
> Sent: Saturday, August 20, 2016 9:56 AM
> To: ap-gto@...
> Subject: Re: [ap-gto] Re: PEC
>
>
>
> "but you may have to invert the PEC curve."
>
> You NEVER have to invert the PEC curve. Calibration is not the same as producing a
> PE curve and uploading it to your mount servo. Let's not confuse the two. Once you
> have done a PE run and uploaded a PE curve to the mount, you should not have to
> do this again for a couple of years. Calibration of your camera for autoguiding is a
> whole other issue. There is no reason to do a PE curve willy nilly every time you set
> up. That is just bonkers.
>
> Another observation: after doing a PE run, you can retrieve the curve that was loaded
> into your mount, and that will tell you whether or not you have done the run
> successfully. It will look just like the curve that you generated and uploaded.
>
> If, after turning PE on, you still get drift in RA, then you probably are not properly
> polar aligned. However, even with perfect polar alignment, the RA axis will still drift
> due to atmospheric refraction. The only place where the exact sidereal rate produces
> no drift is at the zenith. Everywhere else the stars will drift slowly or rapidly depending
> on how far from the horizon you are pointing. The only way to eliminate RA drift (and
> Dec drift) is to model the sky and allow the model to modify the tracking rates.
>
> Is it possible to determine if the RA drift is due to PE or to drift? Yes, but this requires
> a bit of old fashioned experimentation. Drift is constant, PE is cyclical. You can see
> the cyclical motion of PE by offsetting azimuth axis about 5 to 10 degrees and
> recording star drift with your CCD camera for about 13 minutes. You will get two
> worm cycles in your image, and you can then measure the amount of periodic error
> by looking at the cyclical trail of any star in your image. Measuring the number of
> pixel variation of the cycles will give you the amount of PE. If the star streaks are
> basically straight, then there is little or no periodic error. Do this with PEM on and
> PEM off to see the improvement.
>
> Rolando
>
>
> -----Original Message-----
> From: 'Ray Gralak (Groups)' groups3@... [ap-gto] > gto@...>
> To: ap-gto gto@...>
> Sent: Sat, Aug 20, 2016 10:26 am
> Subject: RE: [ap-gto] Re: PEC
>
> Hi Larry,
>
> I think I meant that considering nothing changes (like maybe in a permanent setup).
> More accurately, you will usually need to do the calibration wizard once per night.
> However, if you change equipment or camera orientation then you will need to
> calibrate again. If you do a pier flip, you don't necessarily need to calibrate, but you
> may have to invert the PEC curve.
>
> -Ray Gralak
> Author of APCC (Astro-Physics Command Center): http://www.astro-
> physics.com/index.htm?products/accessories/software/apcc/apcc
> Author of PEMPro: http://www.ccdware.com
> Author of Astro-Physics V2 ASCOM Driver: http://www.gralak.com/apdriver
> Author of PulseGuide: http://www.pulseguide.com
> Author of Sigma: http://www.gralak.com/sigma
>
>
> > -----Original Message-----
> > From: ap-gto@... [mailto:ap-gto@... <mailto:ap-
> gto@...?> ]
> > Sent: Saturday, August 20, 2016 8:08 AM
> > To: ap-gto@...
> > Subject: RE: [ap-gto] Re: PEC
> >
> >
> >
> > Ray, excuse me for butting into this conversation. But the reference you made
> about
> > the Calibration Wizard says you only need to do this once. Is this also true if I
> > remove the telescope/camera and later replace it on the mount (a refractor) and the
> > camera angle is slightly off from its previous position?
> >
> > Larry
> >
> >
>
>
>
> ------------------------------------
> Posted by: "Ray Gralak \(Groups\)" <groups3@...>
> ------------------------------------
>
> To UNSUBSCRIBE, or for general information on the ap-gto list
> see http://groups.yahoo.com/group/ap-gto
> ------------------------------------
>
> Yahoo Groups Links
>
>
>
>
>
>



------------------------------------
Posted by: "Ray Gralak \(Groups\)" <groups3@...>
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Roland Christen
 

It's not that important to get he image scale "exactly" right. If you are off by 10% on a 5 arc second PE curve, the net result is that your compensation with PEM on will be in error by maybe 1/2 arc second. That is well within the noise of the mechanical driving parameters.
 
Rolando
 
 

-----Original Message-----
From: 'Ray Gralak (Groups)' groups3@... [ap-gto]
To: ap-gto
Sent: Sat, Aug 20, 2016 12:27 pm
Subject: RE: [ap-gto] Re: PEC

Hi Joe,

> I have found the scale changes “somewhat”, if I go through ALL the
> calibration steps, on the flip side.

One possible reason for image scale changes could be "settling" of equipment after the pier flip.

Also, the accuracy of the calculated image scale depends on how accurately you click the start and ends of star trails, so there can be some variation. You can try zooming in first to click an endpoint. But, you don't want to click the very last pixels of a trail. The trail has a width and so at each end you want to pick a point 1/2 the trail width from the very ends of the trail.

> It may account for my getting different PEC curve coefficients on
> alternate pier sides.

I have seen this to in my 1200, but I don't think it has anything to do with image scale. It may have something to so with how the worm rides on the worm wheel on each side of the pier when there is a weight imbalance.

-Ray Gralak
Author of APCC (Astro-Physics Command Center): http://www.astro-physics.com/index.htm?products/accessories/software/apcc/apcc
Author of PEMPro: http://www.ccdware.com
Author of Astro-Physics V2 ASCOM Driver: http://www.gralak.com/apdriver
Author of PulseGuide: http://www.pulseguide.com
Author of Sigma: http://www.gralak.com/sigma


> -----Original Message-----
> From: ap-gto@... [mailto:ap-gto@...]
> Sent: Saturday, August 20, 2016 9:05 AM
> To: ap-gto@...
> Subject: Re: [ap-gto] Re: PEC
>
>
>
> Ray,
>
> To your point about calibration after a pier flip. I was thinking it would be better to
> run calibration, but also just SKIP ahead to the step that the user selects the “hockey
> stick” pattern, and changes it “diagonally” to the previous pier side’s calibration run,
> selected one.
>
> That way, the camera is not touched or adjusted, which would change the camera
> angle from the original pier side calibration. I have found the scale changes
> “somewhat”, if I go through ALL the calibration steps, on the flip side. It may account
> for my getting different PEC curve coefficients on alternate pier sides.
>
> Joe
>
>



------------------------------------
Posted by: "Ray Gralak \(Groups\)" <groups3@...>
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Joe Zeglinski
 

Ray,
 
    I agree with all you said.
    Originally, I did rotate the camera, if I wanted to run on the flip side. I really shouldn’t need to, but I was curious if there COULD be any difference on PEC performance (or PEM curve generation), on one or other pier side. I realized, as you said, that a COMPLETE recalibration would have “operator influenced” differences if the CCD was rotated perhaps even a hair less than 180 degrees. I also followed your advice, in a former post, to carefully click the star trail dead center, a sufficient distance away from the star trail's  “rounded” ends.
 
    Even with all such meticulous precautions, the curves were different, rather than a perfect repeat, on a well counter balanced AP-1200. That is when I decided to still try  a “partial re-calibration”, with PemPro Calibration Wizard keeping its “previous pier side”  calculated CCD scale, and simply go DIRECTLY to PemPro Calibration - STEP #4 - to just change the star trail “PATTERN setting”. Then exit the Wizard and start the actual PEM curve data generation run.
 
    Unfortunately, this was quite some months ago, and I didn’t have another chance to check for any possible improvement in curve parameter consistency, used on alternate pier sides.
 
    If the “worm surface” is playing a large part in the curve differences, as I suspected as well, then I hope PemPro will some day have the option of “averaging” collected data from (optionally)  both pier sides, before generating the final curve. Or, alternatively, maybe the user might be allowed to choose a previous data file, as one pier side, and then blend it with the flip side collected data file.
 
    As a test, I was thinking about putting the two Data collection sets into EXCEL columns and generating an Average to a third column, as a new “pseudo-collected” data file for Pempro to use for curve calculation. The result might eliminate the worm-surface dependency, caused by any “counterweight imbalance”.
 
    One benefit might be that I can then totally disregard the effect of cwt imbalance on PEC performance – since I don’t slide the cwts  up & down after every pier flip,  in order to keep a (single-sided) PEC curve relevant.
 
This is NOT urgent, just something I want to confirm.
 
Joe Z.


Roland Christen
 

PE has nothing to do with pier side. It is the cyclical variation of the driving worm against the RA worm wheel. As such, the worm gear knows nothing about pier side, neither does it know where the Dec axis is pointed. Therefore once loaded, the PE compensating curve will simply compensate for the worm rotation - i.e. NOT the worm wheel rotation, just the driving worm gear. It goes around once every 6.4 minutes, regardless of where the Dec axis is pointed, regardless of which tooth on the worm wheel it happens to be attached to at that moment.
 
Rolando
 
 

-----Original Message-----
From: 'Joseph Zeglinski' J.Zeglinski@... [ap-gto]
To: ap-gto
Sent: Sat, Aug 20, 2016 2:08 pm
Subject: Re: [ap-gto] Re: PEC



Ray,
 
    I agree with all you said.
    Originally, I did rotate the camera, if I wanted to run on the flip side. I really shouldn’t need to, but I was curious if there COULD be any difference on PEC performance (or PEM curve generation), on one or other pier side. I realized, as you said, that a COMPLETE recalibration would have “operator influenced” differences if the CCD was rotated perhaps even a hair less than 180 degrees. I also followed your advice, in a former post, to carefully click the star trail dead center, a sufficient distance away from the star trail's  “rounded” ends.
 
    Even with all such meticulous precautions, the curves were different, rather than a perfect repeat, on a well counter balanced AP-1200. That is when I decided to still try  a “partial re-calibration”, with PemPro Calibration Wizard keeping its “previous pier side”  calculated CCD scale, and simply go DIRECTLY to PemPro Calibration - STEP #4 - to just change the star trail “PATTERN setting”. Then exit the Wizard and start the actual PEM curve data generation run.
 
    Unfortunately, this was quite some months ago, and I didn’t have another chance to check for any possible improvement in curve parameter consistency, used on alternate pier sides.
 
    If the “worm surface” is playing a large part in the curve differences, as I suspected as well, then I hope PemPro will some day have the option of “averaging” collected data from (optionally)  both pier sides, before generating the final curve. Or, alternatively, maybe the user might be allowed to choose a previous data file, as one pier side, and then blend it with the flip side collected data file.
 
    As a test, I was thinking about putting the two Data collection sets into EXCEL columns and generating an Average to a third column, as a new “pseudo-collected” data file for Pempro to use for curve calculation. The result might eliminate the worm-surface dependency, caused by any “counterweight imbalance”.
 
    One benefit might be that I can then totally disregard the effect of cwt imbalance on PEC performance – since I don’t slide the cwts  up & down after every pier flip,  in order to keep a (single-sided) PEC curve relevant.
 
This is NOT urgent, just something I want to confirm.
 
Joe Z.



Roland Christen
 

I seem to have done all of this and somehow there is no improvement.
 
When you say no improvement, what do you mean? Let's start with that and try to decipher what you are experiencing.
 
Rolando
 
 
-----Original Message-----
From: salfranc@... [ap-gto]
To: ap-gto
Sent: Sat, Aug 20, 2016 4:57 am
Subject: [ap-gto] Re: PEC



Thank you for all the advise. I seem to have done all of this and somehow there is no improvement.
I am using Pempro as described here, created the curse and then send it to the mount. Then I done a new acquire data with the pem on and there is no improvement.
I have also tried to reverse the curve but still no luck.
Thank you for your help.
Vince




Vince Salfranc
 

Hi Ray,
Thank you for that.
I will go out and try to run the calibration again and them go a new curve.
I will let you know how I get on.
Vince