So, the primary cause of a motor stall is an external mechanical force that is countering the direction that the motors are driving the axes in question. Sometimes it's electrical, such as your power source (such as a battery) furnishing too little voltage to the mount.

Since you didn't mention verifying the physical condition of the mount and the stuff you have hanging off of it, have you checked balance of both RA and dec and looked for any cable wrapping or snags that could be catching and preventing one of the axes from turning past a certain point?

You assertion that the issue might be software-based is misinformed - APCC and the ASCOM driver sends commands to the mount controller to slew and move to the requested point; so the software on your computer is not responsible for actually driving the motors themselves every micrometer of the way. It's impossible for APCC to be directly responsible or the cause of a motor stall.

Describe your mount's load in more details and the work you have done to verify balance, as well as any other mechanical configuration issues that would be the most likely causes of a stall event.

/dale

I'm using APCC Pro version 1.8.3.1 and VCP4-P01-13 firmware.

Hello,

Recently I had a very productive remote session with Howard Hedlund from A-P, who helped me to setup meridian and homing limits. I did some tests following the session and I've got some issues I'd like to raise here:

Thanks Ray.  Here is the pnt file.  It consists of 22 samples along a DEC arc of -15 degrees from HA -3 to the meridian.  With refraction correction turned off the Offset error in HA is -170.12.  With refraction correction disabled the model terms are reasonable numbers.  With refraction correction enabled you will see the model terms go really bad.  So the model seems good without refraction and samples along a DEC arc, but when refraction is turned on the model is off the scale.  Something dramatic happened.  But, if you remove the offset terms then the model is back to being realistic.  Am anxious to see what happened.

Craig

Post your PNT file here for analysis. I'll let you know why your model is acting that way.

-Ray Gralak
Author of APCC (Astro-Physics Command Center): https://www.astro-physics.com/apcc-pro
Author of PEMPro V3: https://www.ccdware.com
Author of Astro-Physics V2 ASCOM Driver: https://www.siriusimaging.com/apdriver

That is  what I said in my first post to this thread, that others are using this temporarily, but it would be useful to summarize the process for others who are not familiar with the technique to try it out on their system.  Which brings me back to my original question, why is it that when I turn on refraction that it throws the Offset error from 100 or so to 100 million or so .. I cannot envisage any change due to refraction that would cause the HA error to jump so high.  It might be a sign that there is problem in the refraction calculation to the model terms.

Craig

Actually, you can try DEC ARC modelling now. It is very simple, fast and easy to setup. Here is what you do:

I believe Dean and a few others have already been creating models that way, so it's nothing new.

It's just that the tracking rates produced from those data points result from a full-sky model. The actual Declination Arc Tracking feature does not even use the full-sky model terms and hasn't been released yet.

-Ray Gralak
Author of APCC (Astro-Physics Command Center): https://www.astro-physics.com/apcc-pro
Author of PEMPro V3: https://www.ccdware.com
Author of Astro-Physics V2 ASCOM Driver: https://www.siriusimaging.com/apdriver

-----Original Message-----
From: main@ap-gto.groups.io [mailto:main@ap-gto.groups.io] On Behalf Of Craig Young
Sent: Thursday, July 30, 2020 9:12 PM
To: main@ap-gto.groups.io
Subject: Re: [ap-gto] APPC refraction correction question

Dean,
Actually, you can try DEC ARC modelling now. It is very simple, fast and easy to setup. Here is what you do:
1. Run APCC (I am running latest version (v1.8.2.1)
2. Click Pointing Model tab
3. Click APPM button
4. Setup APPM as you always do
5. click Measurement Points tab
6. DEC settings:
DEC spacing: 1 degree,
DEC offset: 1 degree,
Min DEC: set this to the DEC arc (e.g., -25 declination),
Max DEC: same number (e.g., -25)

7. RA settings
Right Ascension spacing: 2 degrees (this will define the # samples along the arc to be tested)
RA Offset: 0
Min Hour Angle (east): -3 (set these to the span of the arc)
Max Hour Angle (west): 3

8. Click Show Points button, this will show a map with the DEC arc displayed

You can change the length of the arc and the number of samples along the arc. I found 20 samples or so was
excellent but have also tried 10 points and that works also. So far I have only tried sampling the East sky but on
next clear night will try West sky.

9. Click Start button on Run tab.

It won't take long to measure the samples and when finished it is saved to disk as a .pnt file. You can later change
the name of the pnt file to be something like "DEC ARC -25 degrees". When finished you will be asked to
immediately load the model .. click yes. Your DEC ARC model is now running. You can build up a library of these
and load them as needed. For example, I created a specific DEC ARC for a star cluster and another for a galaxy
where I took lots of images over several nights along the same DEC arc.

Use the GoTo/RECAL tab to move the scope to any point along the DEC arc, e.g., I start at -3 HA. Then begin
imaging .. I can now do 5 minute images with 1 arcsec accuracy. Then, if you enable Refraction Correction you
may notice the tracking rate goes out of whack. Simply disable the top two model terms (Offset Error) in the
Pointing Model tab and you should see the tracking correction go back to normal, but different due to refraction
correction. When I do this I can now do 10 minute images with less than 1 arcsec tracking error.

I suspect Ray's new feature will automate a lot of this, but you can try it out now manually.

Craig

Dean,
Actually, you can try DEC ARC modelling now.  It is very simple, fast and easy to setup.  Here is what you do:
1. Run APCC (I am running latest version (v1.8.2.1)
2. Click Pointing Model tab
3. Click APPM button
4. Setup APPM as you always do
5. click Measurement Points tab
6. DEC settings:
  DEC spacing: 1 degree,
  DEC offset: 1 degree,
  Min DEC: set this to the DEC arc (e.g., -25 declination),
  Max DEC: same number (e.g., -25)

7. RA settings
  Right Ascension spacing: 2 degrees (this will define the # samples along the arc to be tested)
  RA Offset: 0
  Min Hour Angle (east): -3 (set these to the span of the arc)
  Max Hour Angle (west): 3

8. Click Show Points button, this will show a map with the DEC arc displayed

You can change the length of the arc and the number of samples along the arc.  I found 20 samples or so was excellent but have also tried 10 points and that works also.  So far I have only tried sampling the East sky but on next clear night will try West sky.

9. Click Start button on Run tab.

It won't take long to measure the samples and when finished it is saved to disk as a .pnt file.  You can later change the name of the pnt file to be something like "DEC ARC -25 degrees".  When finished you will be asked to immediately load the model .. click yes.  Your DEC ARC model is now running.  You can build up a library of these and load them as needed.  For example, I created a specific DEC ARC for a star cluster and another for a galaxy where I took lots of images over several nights along the same DEC arc.

Use the GoTo/RECAL tab to move the scope to any point along the DEC arc, e.g., I start at -3 HA.  Then begin imaging .. I can now do 5 minute images with 1 arcsec accuracy.  Then, if you enable Refraction Correction you may notice the tracking rate goes out of whack.  Simply disable the top two model terms (Offset Error) in the Pointing Model tab and you should see the tracking correction go back to normal, but different due to refraction correction.  When I do this I can now do 10 minute images with less than 1 arcsec tracking error.

I suspect Ray's new feature will automate a lot of this, but you can try it out now manually.

Craig

Yes, the full sky model works, as evidenced by many unguided images produced with various setups. However, when only a portion of the sky is sampled the accuracy of the model depends on the solidity of the setup and the proper matching of pointing terms to the actual mechanics of the mount.

But the Declination Arc Tracking model is entirely different and is not based on the full sky model's pointing terms.

-Ray Gralak
Author of APCC (Astro-Physics Command Center): https://www.astro-physics.com/apcc-pro
Author of PEMPro V3: https://www.ccdware.com
Author of Astro-Physics V2 ASCOM Driver: https://www.siriusimaging.com/apdriver

On Thu, Jul 30, 2020 at 05:56 PM, Ray Gralak wrote:

First, you are not creating "DEC ARC" models because that version of APCC has not been released.

Now that is interesting.  I will be looking forward to that feature.
 
--
Dean Jacobsen
http://astrophoto.net/wp/
Image Gallery - http://astrophoto.net/wp/image-gallery/
Astrobin - https://www.astrobin.com/users/deanjacobsen/ 

Call it what you want Ray, the fact is it does work, as long as you do not use the Offset Error terms with refraction.  And it is a lot easier to say than "Building an APPM model by sampling only points along a declination arc".  I think the users get the idea.

If enabling refraction changes the model terms then is it correct that APPM goes back through all the sample points and adjusts them for refraction effects?  If so, these would be minor changes, a few arc seconds at most for each sample when sampling above 45 degrees in the sky, and fitting the adjusted data points should still be very close to what the terms are without refraction.  Not the huge changes I see.

Craig

Can anyone, who is using APPM to build DEC ARC models,

First, you are not creating "DEC ARC" models because that version of APCC has not been released. You are creating a full-sky model based on a limited area of the sky.

Second, unchecking/checking any option will re-calculate the best-fit values from the supplied data. "Best-Fit" depends on the quality of the data and how the model terms match the mechanicals. If you have a scope with unmodeled behavior then the terms can vary significantly.

-Ray Gralak
Author of APCC (Astro-Physics Command Center): https://www.astro-physics.com/apcc-pro
Author of PEMPro V3: https://www.ccdware.com
Author of Astro-Physics V2 ASCOM Driver: https://www.siriusimaging.com/apdriver

-----Original Message-----
From: main@ap-gto.groups.io [mailto:main@ap-gto.groups.io] On Behalf Of Craig Young
Sent: Thursday, July 30, 2020 5:38 PM
To: main@ap-gto.groups.io
Subject: Re: [ap-gto] APPC refraction correction question

Can anyone, who is using APPM to build DEC ARC models, confirm that enabling refraction correction changes
the model terms significantly. You can easily run this test during the day by slewing to any location in the sky and
toggling the state of the refraction correction checkbox and noting the change in the Offset Error-Hour Angle term,
located at the top of the model terms list.

I am trying to find out if this is an error in APCC or something in my system. As discovered above, if I remove the
Offset Error term when refraction correction is enabled, then the tracking rates look reasonable. But I am not sure if
refraction correction is now accurate when removing the model term. I thought I would check with others before
reporting this formally as a software error in APCC.

Craig

Can anyone, who is using APPM to build DEC ARC models, confirm that enabling refraction correction changes the model terms significantly. You can easily run this test during the day by slewing to any location in the sky and toggling the state of the refraction correction checkbox and noting the change in the Offset Error-Hour Angle term, located at the top of the model terms list.

I am trying to find out if this is an error in APCC or something in my system.  As discovered above, if I remove the Offset Error term when refraction correction is enabled, then the tracking rates look reasonable. But I am not sure if refraction correction is now accurate when removing the model term.  I thought I would check with others before reporting this formally as a software error in APCC.

Craig

Thanks Ray,

I appreciate there are only so many hours in a day.

I'll have a look at Voyager and fingers crossed their scheduling engine is released in the near future for a Windows solution.

Regards,

DT

Thanks Dean!  I'm going to try this out next time out.  All the best, Scott

I've had my AE's for a few months now but have never checked to see that they are doing what they should be doing.

Do I just run PEMPro - with a proper calibration - (with PEC Off) and watch the line - which should be pretty much flat?