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Tracking issue

Craig Young
 

Setup: AP1600GT w/encoders, APCC Pro (1.7.1.1)


I downloaded the latest version of APCC and then did a 100 point model in the eastern sky only.  After the model was created I then slewed the telescope to RA = -3 hours(HA) and DEC = observatory latitude so the scope would pass through the zenith at the meridian.  60 second images taken every five minutes for 1 hour were captured and then plate solved with Pinpoint (full version) using UCAC4 catalog.


Test 1: modeling and refraction correction turned off.  The drift was RA: -34.12 arcsec, DEC: -36.76 arcsec


Test 2: modeling and refraction correction turned on.  The drift was RA: -30.81 arcsec, DEC: -6.10 arcsec


The modeling correction significantly improved DEC tracking over the one hour but had very little effect in RA.


The telescope is two years old and this RA drift problem has been with it from the start.  Is it possible the RA problem is due to the encoder not calibrated?  Or maybe a time base (crystal) off?  Possibly a related issue is that each time APCC is started the pointing error increases.  So for the first night the pointing error would be 25 arcsec, next night it is 120 arcsec and then the third night something like 350 arcsec.


This telescope is located in the southern hemisphere so maybe that might be confusing the software.


Any ideas on how to diagnose where the problem is?


Craig
Ron Kramer
 

Oh wow - it's suppose to help tracking?  I never bothered with pointing model because I thought it was pointing...  essentially goto's.  And mine are ALWAYS DEAD ON.
I have found that I don't track well. 30+ second subs trail. Which surprises me for the AP mount.  So I guide.   But really - a pointing model will help with tracking?  I hear some people with other mounts doing 10 minute exposures without guiding. I'd be thrilled with a couple minutes without guiding. 

I've abandoned APCC in lu of INDI...  but that's an attractive feature to help lure me back.   I didn't know it would do that. (sorry it's not working for RA too -  yet).


On Sun, Apr 28, 2019 at 4:54 PM craigyoungm8@... [ap-gto] <ap-gto@...> wrote:
 

Setup: AP1600GT w/encoders, APCC Pro (1.7.1.1)


I downloaded the latest version of APCC and then did a 100 point model in the eastern sky only.  After the model was created I then slewed the telescope to RA = -3 hours(HA) and DEC = observatory latitude so the scope would pass through the zenith at the meridian.  60 second images taken every five minutes for 1 hour were captured and then plate solved with Pinpoint (full version) using UCAC4 catalog.


Test 1: modeling and refraction correction turned off.  The drift was RA: -34.12 arcsec, DEC: -36.76 arcsec


Test 2: modeling and refraction correction turned on.  The drift was RA: -30.81 arcsec, DEC: -6.10 arcsec


The modeling correction significantly improved DEC tracking over the one hour but had very little effect in RA.


The telescope is two years old and this RA drift problem has been with it from the start.  Is it possible the RA problem is due to the encoder not calibrated?  Or maybe a time base (crystal) off?  Possibly a related issue is that each time APCC is started the pointing error increases.  So for the first night the pointing error would be 25 arcsec, next night it is 120 arcsec and then the third night something like 350 arcsec.


This telescope is located in the southern hemisphere so maybe that might be confusing the software.


Any ideas on how to diagnose where the problem is?


Craig




--

Roland Christen
 


I have found that I don't track well. 30+ second subs trail.
If you have 30 second subs that trail you have either 1) not polar drift aligned and/or 2) have not turned on PE correction or have never checked your PE correction or 3) you are imaging low in the sky where there is considerable atmospheric refraction (stars move slower there compared to the sidereal tracking rate).

You may also have flexure, this is especially true in SCTs.

Bottom line:

Trailing in RA? check PE correction. Do a proper drift alignment. This will minimize drift for an area up to +- 2 hours RA from the zenith.

Trailing in DEC. Don't blame the mount since DEC is stationary when the scope is simply tracking. Dec drift is always a function of how well you have drift aligned. The whole point of drift alignment is to eliminate Dec drift. If you don't do that, you will have Dec drift and will get trailing.

I'll take any of our mounts, yes even yours, and set it up properly (a proper accurate PE correction turned ON), drift align it, point it to an area around the zenith and guarantee 5 minute exposures with no trailing. PEMPro does a wonderful job to achieve this. Without it you are fishing in puddles.

Rolando


-----Original Message-----
From: Ron Kramer ronkramer1957@... [ap-gto]
To: ap-gto
Sent: Mon, Apr 29, 2019 3:21 pm
Subject: Re: [ap-gto] Tracking issue



Oh wow - it's suppose to help tracking?  I never bothered with pointing model because I thought it was pointing...  essentially goto's.  And mine are ALWAYS DEAD ON.
I have found that I don't track well. 30+ second subs trail. Which surprises me for the AP mount.  So I guide.   But really - a pointing model will help with tracking?  I hear some people with other mounts doing 10 minute exposures without guiding. I'd be thrilled with a couple minutes without guiding. 

I've abandoned APCC in lu of INDI...  but that's an attractive feature to help lure me back.   I didn't know it would do that. (sorry it's not working for RA too -  yet).


On Sun, Apr 28, 2019 at 4:54 PM craigyoungm8@... [ap-gto] <ap-gto@...> wrote:
 
Setup: AP1600GT w/encoders, APCC Pro (1.7.1.1)

I downloaded the latest version of APCC and then did a 100 point model in the eastern sky only.  After the model was created I then slewed the telescope to RA = -3 hours(HA) and DEC = observatory latitude so the scope would pass through the zenith at the meridian.  60 second images taken every five minutes for 1 hour were captured and then plate solved with Pinpoint (full version) using UCAC4 catalog.

Test 1: modeling and refraction correction turned off.  The drift was RA: -34.12 arcsec, DEC: -36.76 arcsec

Test 2: modeling and refraction correction turned on.  The drift was RA: -30.81 arcsec, DEC: -6.10 arcsec

The modeling correction significantly improved DEC tracking over the one hour but had very little effect in RA.

The telescope is two years old and this RA drift problem has been with it from the start.  Is it possible the RA problem is due to the encoder not calibrated?  Or maybe a time base (crystal) off?  Possibly a related issue is that each time APCC is started the pointing error increases.  So for the first night the pointing error would be 25 arcsec, next night it is 120 arcsec and then the third night something like 350 arcsec.

This telescope is located in the southern hemisphere so maybe that might be confusing the software.

Any ideas on how to diagnose where the problem is?

Craig



--


Craig Young
 

Last night I turned off the APCC tracking and pointing correction function and then recorded 10 consecutive 60 second images at RA -3 hours (HA) and DEC 0 degrees.  Using Pinpoint I then measured the drift over the imaging time (approx 11 minutes) and calculated the drive corrections:

  RA drift: 19.64 arcsec
  DEC drift: 7.31 arcsec
  calculated RA tracking rate correction: -0.00190 RA seconds/sidereal second
  calculated DEC tracking rate correction: 0.01080 arcsec/second

I slewed the telescope back to the starting point and put the tracking rate corrections into the V2 driver as custom rates.  Repeating the test I now got:

  RA drift: 0.36 arcsec
  DEC drift: 0.43 arcsec

which is a significant improvement in tracking.

I then slewed back to the starting point and did a 10 minute unguided exposure.  The image showed perfectly round stars.

This showed that with the correct tracking rates the AP mount can produce perfect 10 minute unguided images.  So the tracking rates at this position in the sky must be:
  RA: -0.00190  RA seconds/sidereal second
  DEC: +0.01080 arcsec/second

With APCC tracking correction enabled the tracking corrections at this location in the sky are:

  RA: 0.00152 RA seconds/sidereal second
  DEC: +0.01000 arcsec/second

Notice the APCC RA tracking correction is opposite the sign of the known correct tracking correction rate from above but about the correct magnitude (152 vs 190).

The APCC DEC tracking correction is the right sign and also about the correct magnitude (1000 vs 1080).

This is consistent with my first posting results which showed no improvement in RA tracking when using the model, but significant improvement in DEC tracking.  I suspect there is a sign reversal error in calculating the tracking rates for RA.  Maybe this is only for the southern hemisphere and explains why users in the northern hemisphere are not seeing this problem.

Craig
Roland Christen
 

Hello Craig,

Thank you for doing this test. I was hoping that Howard could see your posts and I was going to consult with him about your results. Unfortunately Howard is home with the Flu and cannot come in for the next few days. Your tests give a big clue as to what is happening and i will consult with our software guy tomorrow to see what can be done and why the sign is backwards.

Thanks again,

Rolando



-----Original Message-----
From: craigyoungm8@... [ap-gto]
To: ap-gto
Sent: Mon, Apr 29, 2019 5:37 pm
Subject: Re: [ap-gto] Tracking issue



Last night I turned off the APCC tracking and pointing correction function and then recorded 10 consecutive 60 second images at RA -3 hours (HA) and DEC 0 degrees.  Using Pinpoint I then measured the drift over the imaging time (approx 11 minutes) and calculated the drive corrections:

  RA drift: 19.64 arcsec
  DEC drift: 7.31 arcsec
  calculated RA tracking rate correction: -0.00190 RA seconds/sidereal second
  calculated DEC tracking rate correction: 0.01080 arcsec/second

I slewed the telescope back to the starting point and put the tracking rate corrections into the V2 driver as custom rates.  Repeating the test I now got:

  RA drift: 0.36 arcsec
  DEC drift: 0.43 arcsec

which is a significant improvement in tracking.

I then slewed back to the starting point and did a 10 minute unguided exposure.  The image showed perfectly round stars.

This showed that with the correct tracking rates the AP mount can produce perfect 10 minute unguided images.  So the tracking rates at this position in the sky must be:
  RA: -0.00190  RA seconds/sidereal second
  DEC: +0.01080 arcsec/second

With APCC tracking correction enabled the tracking corrections at this location in the sky are:

  RA: 0.00152 RA seconds/sidereal second
  DEC: +0.01000 arcsec/second

Notice the APCC RA tracking correction is opposite the sign of the known correct tracking correction rate from above but about the correct magnitude (152 vs 190).

The APCC DEC tracking correction is the right sign and also about the correct magnitude (1000 vs 1080).

This is consistent with my first posting results which showed no improvement in RA tracking when using the model, but significant improvement in DEC tracking.  I suspect there is a sign reversal error in calculating the tracking rates for RA.  Maybe this is only for the southern hemisphere and explains why users in the northern hemisphere are not seeing this problem.

Craig
Ray Gralak
 

Hi Craig,

Notice the APCC RA tracking correction is opposite the sign of the known correct tracking correction rate from
above but about the correct magnitude (152 vs 190).
If you open APCC's Tracking Rate Debug window you can easily invert the RA direction. In fact maybe it is already inverted as APCC will remember the setting between application starts.

That said, the pointing model is a "best fit" model of the data given to it. The model minimizes the error across all of the data points. Minimizing the error doesn't mean pointing and tracking will be perfect. Most often it is not going to be perfect, especially in heavier mirrored scopes and also in locations where temperature varies widely from the temperature at which the data was originally collected.

Best regards,

-Ray Gralak
Author of APCC (Astro-Physics Command Center): http://www.astro-physics.com/index.htm?products/accessories/software/apcc/apcc
Author of PEMPro V3: https://www.ccdware.com
Author of Astro-Physics V2 ASCOM Driver: https://www.siriusimaging.com/apdriver


-----Original Message-----
From: ap-gto@... [mailto:ap-gto@...]
Sent: Monday, April 29, 2019 3:38 PM
To: ap-gto@...
Subject: Re: [ap-gto] Tracking issue



Last night I turned off the APCC tracking and pointing correction function and then recorded 10 consecutive 60
second images at RA -3 hours (HA) and DEC 0 degrees. Using Pinpoint I then measured the drift over the imaging
time (approx 11 minutes) and calculated the drive corrections:

RA drift: 19.64 arcsec

DEC drift: 7.31 arcsec

calculated RA tracking rate correction: -0.00190 RA seconds/sidereal second
calculated DEC tracking rate correction: 0.01080 arcsec/second

I slewed the telescope back to the starting point and put the tracking rate corrections into the V2 driver as custom
rates. Repeating the test I now got:

RA drift: 0.36 arcsec
DEC drift: 0.43 arcsec

which is a significant improvement in tracking.


I then slewed back to the starting p oint and did a 10 minute unguided exposure. The image showed perfectly round
stars.

This showed that with the correct tracking rates the AP mount can produce perfect 10 minute unguided images. So
the tracking rates at this position in the sky must be:
RA: -0.00190 RA seconds/sidereal second

DEC: +0.01080 arcsec/second

With APCC tracking correction enabled the tracking corrections at this location in the sky are:

RA: 0.00152 RA seconds/sidereal second

DEC: +0.01000 arcsec/second

Notice the APCC RA tracking correction is opposite the sign of the known correct tracking correction rate from
above but about the correct magnitude (152 vs 190).

The APCC DEC tracking correction is the right sign and also about the correct magnitude (1000 vs 1080).

This is con sistent with my first posting results which showed no improvement in RA tracking when using the model,
but significant improvement in DEC tracking. I suspect there is a sign reversal error in calculating the tracking rates
for RA. Maybe this is only for the southern hemisphere and explains why users in the northern hemisphere are not
seeing this problem.

Craig
Craig Young
 

Hi Ray,

I opened the Tracking rate debug window and all of the boxes were unchecked.  If I check the invert RA box the tracking correction value does move closer to the correct value rather than away from it.  Any idea why this box has to be checked?  Knowing the root cause may identify the difference in magnitude.  Otherwise, I would agree that the model can only be as good as the data input to it.  Some possible scenarios:

a) a sign problem when the data is imported into the model means the data is good but the derivation of the model terms would be in error and hence a poor model result when applied to tracking,

b) a sign problem in the derivation of the model, also means the data is good but a bad result

c) a sign problem when executing the model, here the data is good and the model is good but the result is bad.

So I think we need to first identify the source of the sign problem and then work on the magnitude problem.

I did compare the inverted RA tracking correction values for various declinations with the known correct values and both provided nearly the same slope but a different zero point.  Which means if a constant is added to the model I was able to map the model correction values with the known correction values quite well.  Researching the difference in the zero point would be a waste of time for everyone but it is good to know the two curve fits are close.

Let me know when you find why the reversal of the sign is needed for RA.  If you want, I can send you my appm model file and if you try it for -3H RA and 0 DEC you will see the sign problem.  From there you might be able to work backwards to identify the problem.

Craig
Craig Young
 

Ray,

I forgot to mention, you can do all these tests indoors on a mount, you do not need the night sky.  The way I test is at night I imaged the sky and got the actual tracking rate corrections needed.  I then tested that with long exposures to verify it was right.  Then, the next day I slew the telescope to those same coordinates and look at the RA correction rate.  It is the wrong sign.  So you won't need clear nights or observing time to verify this and track it down.

Craig
Ray Gralak
 

Hi Craig,

Some possible scenarios:
Or bad data, or random errors, or unmodeled pointing errors.

Have you tried doing a verify run to see how well the model works?

Also, make sure you have created the model you are using with APPM v1.7.1.1 and not an earlier version.

-Ray Gralak
Author of APCC (Astro-Physics Command Center): http://www.astro-physics.com/index.htm?products/accessories/software/apcc/apcc
Author of PEMPro V3: https://www.ccdware.com
Author of Astro-Physics V2 ASCOM Driver: https://www.siriusimaging.com/apdriver


-----Original Message-----
From: ap-gto@... [mailto:ap-gto@...]
Sent: Monday, April 29, 2019 10:06 PM
To: ap-gto@...
Subject: RE: [ap-gto] Tracking issue



Hi Ray,

I opened the Tracking rate debug window and all of the boxes were unchecked. If I check the invert RA box the
tracking correction value does move closer to the correct value rather than away from it. Any idea why this box has
to be checked? Knowing the root cause may identify the difference in magnitude. Otherwise, I would agree that the
model can only be as good as the data input to it. Some possible scenarios:

a) a sign problem when the data is imported into the model means the data is good but the derivation of the model
terms would be in error and hence a poor model result when applied to tracking,

b) a sign problem in the derivation of the model, also means the data is good but a bad result

c) a sign problem when executing the model, here the data is good and the model is good but the result is bad.

So I think we need to first identify the source of the sign problem and then work on the magnitude problem.

I did compare the inverted RA tracking correction values for various declinations with the known correct values and
both provided nearly the same slope but a different zero point. Which means if a constant is added to the model I
was able to map the model correction values with the known correction values quite well. Researching the
difference in the zero point would be a waste of time for everyone but it is good to know the two curve fits are close.

Let me know when you find why the reversal of the sign is needed for RA. If you want, I can send you my appm
model file and if you try it for -3H RA and 0 DEC you will see the sign problem. From there you might be able to
work backwards to identify the problem.

Craig
Ray Gralak
 

Hi Craig,

I forgot to mention, you can do all these tests indoors on a mount, you do not need the night sky. The way I test is
at night I imaged the sky and got the actual tracking rate corrections needed. I then tested that with long exposures
to verify it was right. Then, the next day I slew the telescope to those same coordinates and look at the RA
correction rate. It is the wrong sign. So you won't need clear nights or observing time to verify this and track it
down.
If there is a sign error in RA, perhaps because you are in the Southern Hemisphere, it will be easy to fix. Until then you should be able to enable the Invert RA checkbox and that would have exactly the same as a software fix.

That said, matching a user's pointing model to the mechanical nature of the mount is very complex and every system is different. APCC's telescope model finds the "best fit" of the data collected during an APPM run. As I said it doesn't mean that it will be perfect all-sky, but it should be better.

One thing you can do to check the pointing model's accuracy is to do a Verify run in APPM. This will leave pointing and tracking rate correction enabled and measure the pointing error throughout the sky. Its purpose is to measure how accurately the model matches the mechanical characteristics of your setup. It is important that the pointing model accurately reflects your setup because that is what is used for determining the tracking rate. A poorly matched model could even produce what appears to be an inverted RA tracking rate.

Best regards,

-Ray Gralak
Author of APCC (Astro-Physics Command Center): http://www.astro-physics.com/index.htm?products/accessories/software/apcc/apcc
Author of PEMPro V3: https://www.ccdware.com
Author of Astro-Physics V2 ASCOM Driver: https://www.siriusimaging.com/apdriver


-----Original Message-----
From: ap-gto@... [mailto:ap-gto@...]
Sent: Monday, April 29, 2019 10:08 PM
To: ap-gto@...
Subject: RE: [ap-gto] Tracking issue



Ray,

I forgot to mention, you can do all these tests indoors on a mount, you do not need the night sky. The way I test is
at night I imaged the sky and got the actual tracking rate corrections needed. I then tested that with long exposures
to verify it was right. Then, the next day I slew the telescope to those same coordinates and look at the RA
correction rate. It is the wrong sign. So you won't need clear nights or observing time to verify this and track it
down.

Craig
Ron Kramer
 

Rolando,
I'll check things again, but I'm in a permanent setup and last time I corrected drift - I had it dead on all the way across... but I'll check it again.
6" APO (cf) tube.  guiding in PHD2 on windows averages around .35 total rms err.

PEC I have on... but not sure if it's still valid. I recorded it with ascom - and now I'm using INDI.  (is that retained in the mount?)  
I have PemPro - but after spending a night trying to use it... I haven't looked back at it since. Totally confused and the instructions didn't follow my options. (version change?) Dunno.

But I must guide.  Then all is well.
see? 
https://www.flickr.com/photos/158199519@N08/  


On Mon, Apr 29, 2019 at 4:33 PM chris1011@... [ap-gto] <ap-gto@...> wrote:
 


I have found that I don't track well. 30+ second subs trail.
If you have 30 second subs that trail you have either 1) not polar drift aligned and/or 2) have not turned on PE correction or have never checked your PE correction or 3) you are imaging low in the sky where there is considerable atmospheric refraction (stars move slower there compared to the sidereal tracking rate).

You may also have flexure, this is especially true in SCTs.

Bottom line:

Trailing in RA? check PE correction. Do a proper drift alignment. This will minimize drift for an area up to +- 2 hours RA from the zenith.

Trailing in DEC. Don't blame the mount since DEC is stationary when the scope is simply tracking. Dec drift is always a function of how well you have drift aligned. The whole point of drift alignment is to eliminate Dec drift. If you don't do that, you will have Dec drift and will get trailing.

I'll take any of our mounts, yes even yours, and set it up properly (a proper accurate PE correction turned ON), drift align it, point it to an area around the zenith and guarantee 5 minute exposures with no trailing. PEMPro does a wonderful job to achieve this. Without it you are fishing in puddles.

Rolando


-----Original Message-----
From: Ron Kramer ronkramer1957@... [ap-gto] <ap-gto@...>
To: ap-gto <ap-gto@...>
Sent: Mon, Apr 29, 2019 3:21 pm
Subject: Re: [ap-gto] Tracking issue



Oh wow - it's suppose to help tracking?  I never bothered with pointing model because I thought it was pointing...  essentially goto's.  And mine are ALWAYS DEAD ON.
I have found that I don't track well. 30+ second subs trail. Which surprises me for the AP mount.  So I guide.   But really - a pointing model will help with tracking?  I hear some people with other mounts doing 10 minute exposures without guiding. I'd be thrilled with a couple minutes without guiding. 

I've abandoned APCC in lu of INDI...  but that's an attractive feature to help lure me back.   I didn't know it would do that. (sorry it's not working for RA too -  yet).


On Sun, Apr 28, 2019 at 4:54 PM craigyoungm8@... [ap-gto] <ap-gto@...> wrote:
 
Setup: AP1600GT w/encoders, APCC Pro (1.7.1.1)

I downloaded the latest version of APCC and then did a 100 point model in the eastern sky only.  After the model was created I then slewed the telescope to RA = -3 hours(HA) and DEC = observatory latitude so the scope would pass through the zenith at the meridian.  60 second images taken every five minutes for 1 hour were captured and then plate solved with Pinpoint (full version) using UCAC4 catalog.

Test 1: modeling and refraction correction turned off.  The drift was RA: -34.12 arcsec, DEC: -36.76 arcsec

Test 2: modeling and refraction correction turned on.  The drift was RA: -30.81 arcsec, DEC: -6.10 arcsec

The modeling correction significantly improved DEC tracking over the one hour but had very little effect in RA.

The telescope is two years old and this RA drift problem has been with it from the start.  Is it possible the RA problem is due to the encoder not calibrated?  Or maybe a time base (crystal) off?  Possibly a related issue is that each time APCC is started the pointing error increases.  So for the first night the pointing error would be 25 arcsec, next night it is 120 arcsec and then the third night something like 350 arcsec.

This telescope is located in the southern hemisphere so maybe that might be confusing the software.

Any ideas on how to diagnose where the problem is?

Craig



--




--

Roland Christen
 


I recorded it with ascom - and now I'm using INDI.  (is that retained in the mount?) 
Is that retained in the mount? Only if the PE curve is generated and saved to the mount, otherwise no, nothing is retained unless saved to the mount. If you don't save data, how could it be retained?

If you have no drift, then you have no drift and stars will be round. The fact that stars are not round means you have drift. Or you have no valid PE curve. PEMPro is easy to use, even a caveman like me has figured it out. It really is the only way to create a valid PE curve.

Roland


-----Original Message-----
From: Ron Kramer ronkramer1957@... [ap-gto] <ap-gto@...>
To: ap-gto
Sent: Wed, May 1, 2019 11:58 am
Subject: Re: [ap-gto] Tracking issue



Rolando,
I'll check things again, but I'm in a permanent setup and last time I corrected drift - I had it dead on all the way across... but I'll check it again.
6" APO (cf) tube.  guiding in PHD2 on windows averages around .35 total rms err.

PEC I have on... but not sure if it's still valid. I recorded it with ascom - and now I'm using INDI.  (is that retained in the mount?)  
I have PemPro - but after spending a night trying to use it... I haven't looked back at it since. Totally confused and the instructions didn't follow my options. (version change?) Dunno.

But I must guide.  Then all is well.
see? 
https://www.flickr.com/photos/158199519@N08/  


On Mon, Apr 29, 2019 at 4:33 PM chris1011@... [ap-gto] <ap-gto@...> wrote:
 

I have found that I don't track well. 30+ second subs trail.
If you have 30 second subs that trail you have either 1) not polar drift aligned and/or 2) have not turned on PE correction or have never checked your PE correction or 3) you are imaging low in the sky where there is considerable atmospheric refraction (stars move slower there compared to the sidereal tracking rate).

You may also have flexure, this is especially true in SCTs.

Bottom line:

Trailing in RA? check PE correction. Do a proper drift alignment. This will minimize drift for an area up to +- 2 hours RA from the zenith.

Trailing in DEC. Don't blame the mount since DEC is stationary when the scope is simply tracking. Dec drift is always a function of how well you have drift aligned. The whole point of drift alignment is to eliminate Dec drift. If you don't do that, you will have Dec drift and will get trailing.

I'll take any of our mounts, yes even yours, and set it up properly (a proper accurate PE correction turned ON), drift align it, point it to an area around the zenith and guarantee 5 minute exposures with no trailing. PEMPro does a wonderful job to achieve this. Without it you are fishing in puddles.

Rolando


-----Original Message-----
From: Ron Kramer ronkramer1957@... [ap-gto] <ap-gto@...>
To: ap-gto <ap-gto@...>
Sent: Mon, Apr 29, 2019 3:21 pm
Subject: Re: [ap-gto] Tracking issue



Oh wow - it's suppose to help tracking?  I never bothered with pointing model because I thought it was pointing...  essentially goto's.  And mine are ALWAYS DEAD ON.
I have found that I don't track well. 30+ second subs trail. Which surprises me for the AP mount.  So I guide.   But really - a pointing model will help with tracking?  I hear some people with other mounts doing 10 minute exposures without guiding. I'd be thrilled with a couple minutes without guiding. 

I've abandoned APCC in lu of INDI...  but that's an attractive feature to help lure me back.   I didn't know it would do that. (sorry it's not working for RA too -  yet).


On Sun, Apr 28, 2019 at 4:54 PM craigyoungm8@... [ap-gto] <ap-gto@yahoogroups..com> wrote:
 
Setup: AP1600GT w/encoders, APCC Pro (1.7.1.1)

I downloaded the latest version of APCC and then did a 100 point model in the eastern sky only.  After the model was created I then slewed the telescope to RA = -3 hours(HA) and DEC = observatory latitude so the scope would pass through the zenith at the meridian.  60 second images taken every five minutes for 1 hour were captured and then plate solved with Pinpoint (full version) using UCAC4 catalog.

Test 1: modeling and refraction correction turned off.  The drift was RA: -34.12 arcsec, DEC: -36.76 arcsec

Test 2: modeling and refraction correction turned on.  The drift was RA: -30.81 arcsec, DEC: -6.10 arcsec

The modeling correction significantly improved DEC tracking over the one hour but had very little effect in RA.

The telescope is two years old and this RA drift problem has been with it from the start.  Is it possible the RA problem is due to the encoder not calibrated?  Or maybe a time base (crystal) off?  Possibly a related issue is that each time APCC is started the pointing error increases.  So for the first night the pointing error would be 25 arcsec, next night it is 120 arcsec and then the third night something like 350 arcsec.

This telescope is located in the southern hemisphere so maybe that might be confusing the software.

Any ideas on how to diagnose where the problem is?

Craig



--


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