#APCC - V1.9 Tracking Error #APCC


Rouz
 

I'm very happy that V1.9 now works with NINA and ASTAP.
Model building was very straightforward and quick.

For some reason, my unguided exposures have trailing stars. 
The target will move a few hundred pixels over the coarse of the night.

Using the AP1100CP4, no encoders, CDK12 OTA, pier bolted to concrete floor in a remote dome (backyard).  1700mm focal length,  0.92 arcsec/pixel (bin2)

Mechanical:
I've double checked every bolt from the concrete to the focuser. The system is very rigid, mirror is bonded to permanent cell. Payload is about 70lbs. 
I also pointed near zenith to eliminate any potential sag with the same inconsistent results.

Periodic Error:
Unlikely as the image is constantly moving in on direction. I checked the mount with Pempro last year with a native error of 3" peak to peak. It was about 1" with PEC on.

Model:
Using NINA and ASTAP with "high precision slews" = on
1st attempt with points every 12 degrees
2nd attempt with very fine 6 degrees apart  184 points (I only have half the sky visible)
Environmental sensor, pressure for local weather station.
Its using a sensor on the telescope which was reading RH a bit higher (92 to 99%) than the weather station value of 82%

Tracking:
It seems when I turn Dec-arc tracking on it gets worse.
I tied refraction correction on - off.
Both on both off
Some subs much worse than others, but moves in the same direction generally.

Here is a folder with some 300s test subs, log file, appm files. I have named them with dec arc and refraction correction on or off
https://www.dropbox.com/sh/80ktuhbtr8btnd9/AAB0FKWeeW9S1S4bp2ZHzMsma?dl=0




Any help would be much appreciated as I've been trying to solve this for days non-stop.

Thanks,

Rouz


Ray Gralak
 

Hi Rouz,

Thanks for the details!

Could you also put a zip file created using the APCC Log zipper utility? Please include all the APCC, APPM, and ASCOM logs from the evening when you were doing the imaging.

BTW, I see you are using a dome. When you used APPM did you use the "Hour Angle" strategy for accumulating the data points?

-Ray

-----Original Message-----
From: main@ap-gto.groups.io [mailto:main@ap-gto.groups.io] On Behalf Of roozbeh_bid
Sent: Friday, August 20, 2021 12:10 PM
To: main@ap-gto.groups.io
Subject: [ap-gto] #APCC - V1.9 Tracking Error

I'm very happy that V1.9 now works with NINA and ASTAP.
Model building was very straightforward and quick.

For some reason, my unguided exposures have trailing stars.
The target will move a few hundred pixels over the coarse of the night.

Using the AP1100CP4, no encoders, CDK12 OTA, pier bolted to concrete floor in a remote dome (backyard).
1700mm focal length, 0.92 arcsec/pixel (bin2)

Mechanical:
I've double checked every bolt from the concrete to the focuser. The system is very rigid, mirror is bonded to
permanent cell. Payload is about 70lbs.
I also pointed near zenith to eliminate any potential sag with the same inconsistent results.

Periodic Error:
Unlikely as the image is constantly moving in on direction. I checked the mount with Pempro last year with a native
error of 3" peak to peak. It was about 1" with PEC on.

Model:
Using NINA and ASTAP with "high precision slews" = on
1st attempt with points every 12 degrees
2nd attempt with very fine 6 degrees apart 184 points (I only have half the sky visible)
Environmental sensor, pressure for local weather station.
Its using a sensor on the telescope which was reading RH a bit higher (92 to 99%) than the weather station value
of 82%

Tracking:
It seems when I turn Dec-arc tracking on it gets worse.
I tied refraction correction on - off.
Both on both off
Some subs much worse than others, but moves in the same direction generally.

Here is a folder with some 300s test subs, log file, appm files. I have named them with dec arc and refraction
correction on or off
https://www.dropbox.com/sh/80ktuhbtr8btnd9/AAB0FKWeeW9S1S4bp2ZHzMsma?dl=0




Any help would be much appreciated as I've been trying to solve this for days non-stop.

Thanks,

Rouz



Roland Christen
 


The target will move a few hundred pixels over the coarse of the night.
Did the target move in RA or Dec?

Roland


-----Original Message-----
From: roozbeh_bid <rbidshahri@...>
To: main@ap-gto.groups.io
Sent: Fri, Aug 20, 2021 2:10 pm
Subject: [ap-gto] #APCC - V1.9 Tracking Error

I'm very happy that V1.9 now works with NINA and ASTAP.
Model building was very straightforward and quick.

For some reason, my unguided exposures have trailing stars. 
The target will move a few hundred pixels over the coarse of the night.

Using the AP1100CP4, no encoders, CDK12 OTA, pier bolted to concrete floor in a remote dome (backyard).  1700mm focal length,  0.92 arcsec/pixel (bin2)

Mechanical:
I've double checked every bolt from the concrete to the focuser. The system is very rigid, mirror is bonded to permanent cell. Payload is about 70lbs. 
I also pointed near zenith to eliminate any potential sag with the same inconsistent results.

Periodic Error:
Unlikely as the image is constantly moving in on direction. I checked the mount with Pempro last year with a native error of 3" peak to peak. It was about 1" with PEC on.

Model:
Using NINA and ASTAP with "high precision slews" = on
1st attempt with points every 12 degrees
2nd attempt with very fine 6 degrees apart  184 points (I only have half the sky visible)
Environmental sensor, pressure for local weather station.
Its using a sensor on the telescope which was reading RH a bit higher (92 to 99%) than the weather station value of 82%

Tracking:
It seems when I turn Dec-arc tracking on it gets worse.
I tied refraction correction on - off.
Both on both off
Some subs much worse than others, but moves in the same direction generally.

Here is a folder with some 300s test subs, log file, appm files. I have named them with dec arc and refraction correction on or off
https://www.dropbox.com/sh/80ktuhbtr8btnd9/AAB0FKWeeW9S1S4bp2ZHzMsma?dl=0




Any help would be much appreciated as I've been trying to solve this for days non-stop.

Thanks,

Rouz


--
Roland Christen
Astro-Physics


Rouz
 

Hi Ray,

Yes I used "Hour Angle" with APPM.

I closed APCC, I'll open it again and see if I can create that zip file now.

Thanks,

Rouz


Rouz
 

Hi Roland,

My camera orientation is 90 degrees and the image downwards mostly but at a slight diagonal.

I have made a short video clip in the folder.

https://www.dropbox.com/s/sf8gkmj1ks2c2pu/tracking.wmv?dl=0





Resolution ............... 0.929 arcsec/px

Rotation ................. 90.992 deg

Reference system ......... ICRS

Observation start time ... 2021-08-20 09:29:15 UTC

Observation end time ..... 2021-08-20 09:34:15 UTC

Geodetic coordinates ..... 123 ** 44 W 49 ** 45 N 0 m

Focal distance ........... 1670.25 mm

Pixel size ............... 7.52 um

Field of view ............ 48' 23.0" x 32' 19.1"

Image center ............. RA: 20 11 57.317 Dec: +38 22 29.95


Ray Gralak
 

Rouz,

Unfortunately, I think the "Hour Angle" point ordering strategy may be the problem. Because the points are not collected in a declination-arc it is way more likely to be subject to random flexure at each declination.

Did you try taking any images with all pointing terms enabled but with Declination Arc tracking off?

-Ray

-----Original Message-----
From: main@ap-gto.groups.io [mailto:main@ap-gto.groups.io] On Behalf Of Rouz
Sent: Friday, August 20, 2021 12:54 PM
To: main@ap-gto.groups.io
Subject: Re: [ap-gto] #APCC - V1.9 Tracking Error

Hi Ray,

Yes I used "Hour Angle" with APPM.

I closed APCC, I'll open it again and see if I can create that zip file now.

Thanks,

Rouz


Roland Christen
 

Can you tell me which way the image drifts, RA or Dec?

Roland



-----Original Message-----
From: Rouz <rbidshahri@...>
To: main@ap-gto.groups.io
Sent: Fri, Aug 20, 2021 3:02 pm
Subject: Re: [ap-gto] #APCC - V1.9 Tracking Error

Hi Roland,

My camera orientation is 90 degrees and the image downwards mostly but at a slight diagonal.

I have made a short video clip in the folder.

https://www.dropbox.com/s/sf8gkmj1ks2c2pu/tracking.wmv?dl=0





Resolution ............... 0.929 arcsec/px
Rotation ................. 90.992 deg
Reference system ......... ICRS
Observation start time ... 2021-08-20 09:29:15 UTC
Observation end time ..... 2021-08-20 09:34:15 UTC
Geodetic coordinates ..... 123 ** 44 W 49 ** 45 N 0 m
Focal distance ........... 1670.25 mm
Pixel size ............... 7.52 um
Field of view ............ 48' 23.0" x 32' 19.1"
Image center ............. RA: 20 11 57.317 Dec: +38 22 29.95

--
Roland Christen
Astro-Physics


Rouz
 

Here is another blink clip of the previous nights tracking with a model with less points.

I believe its not a flex problem as its very consistent.


https://www.dropbox.com/s/ke6l2foort7jpod/tracking%2018-Aug-21.wmv?dl=0


Rouz
 

Ray,

Ah, so I shouldn't use "hour angle", I can try that.

I tried pointing corrections on and Dec Arc off, seemed better.

It looked like Dec arc made it worse but the object still moves. Some subs more than others.



Roland Christen
 

You didn't answer my question. Which axis is showing the error?

Roland



-----Original Message-----
From: Rouz <rbidshahri@...>
To: main@ap-gto.groups.io
Sent: Fri, Aug 20, 2021 3:17 pm
Subject: Re: [ap-gto] #APCC - V1.9 Tracking Error

Ray,

Ah, so I shouldn't use "hour angle", I can try that.

I tried pointing corrections on and Dec Arc off, seemed better.

It looked like Dec arc made it worse but the object still moves. Some subs more than others.



--
Roland Christen
Astro-Physics


Rouz
 

Also, I suspect polar alignment isn't perfect. Could that be the cause.

The model can correct for that right? To what degree.

Is that polar az and polar Alt values in the model?


Roland Christen
 

If you can answer my question I could probably tell you what's happening.

Roland



-----Original Message-----
From: Rouz <rbidshahri@...>
To: main@ap-gto.groups.io
Sent: Fri, Aug 20, 2021 3:22 pm
Subject: Re: [ap-gto] #APCC - V1.9 Tracking Error

Also, I suspect polar alignment isn't perfect. Could that be the cause.

The model can correct for that right? To what degree.

Is that polar az and polar Alt values in the model?

--
Roland Christen
Astro-Physics


Ray Gralak
 

I believe its not a flex problem as its very consistent.
It's good that it is consistent, but it is possible that it is unmodeled flexure. The pointing terms best model a solid object with consistent flexure characteristics. When you have a large mirror on one end of the scope the flexure can be uneven as a whole across the scope.

That's what the dec-arc tracking is supposed to handle but the path that the hour-angle point creation strategy takes can introduce random flexures that are not there when doing a declination arc.

-Ray

-----Original Message-----
From: main@ap-gto.groups.io [mailto:main@ap-gto.groups.io] On Behalf Of Rouz
Sent: Friday, August 20, 2021 1:08 PM
To: main@ap-gto.groups.io
Subject: Re: [ap-gto] #APCC - V1.9 Tracking Error

Here is another blink clip of the previous nights tracking with a model with less points.

I believe its not a flex problem as its very consistent.


https://www.dropbox.com/s/ke6l2foort7jpod/tracking%2018-Aug-21.wmv?dl=0


Roland Christen
 

It's not a flex problem, Ray.

Roland



-----Original Message-----
From: Ray Gralak <iogroups@...>
To: main@ap-gto.groups.io
Sent: Fri, Aug 20, 2021 3:31 pm
Subject: Re: [ap-gto] #APCC - V1.9 Tracking Error

> I believe its not a flex problem as its very consistent.

It's good that it is consistent, but it is possible that it is unmodeled flexure. The pointing terms best model a solid object with consistent flexure characteristics. When you have a large mirror on one end of the scope the flexure can be uneven as a whole across the scope.

That's what the dec-arc tracking is supposed to handle but the path that the hour-angle point creation strategy takes can introduce random flexures that are not there when doing a declination arc.

-Ray

> -----Original Message-----
> From: main@ap-gto.groups.io [mailto:main@ap-gto.groups.io] On Behalf Of Rouz
> Sent: Friday, August 20, 2021 1:08 PM
> To: main@ap-gto.groups.io
> Subject: Re: [ap-gto] #APCC - V1.9 Tracking Error
>
> Here is another blink clip of the previous nights tracking with a model with less points.
>
> I believe its not a flex problem as its very consistent.
>
>
> https://www.dropbox.com/s/ke6l2foort7jpod/tracking%2018-Aug-21.wmv?dl=0
>
>







--
Roland Christen
Astro-Physics


Bill Long
 

This is unguided imaging right? If so as a best practice I dial in my PA as close as I can with SharpCap before I build the model. When I was not using encoders I would ensure my PEC curve was solid (~1" or less) using PEMPro and build a new curve if it was no longer correcting as well. Also switch your balancing to neutral in both axis of you haven't already.

Not saying any of these are the cause, just some things to do if you're trying to image unguided.


From: main@ap-gto.groups.io <main@ap-gto.groups.io> on behalf of Rouz <rbidshahri@...>
Sent: Friday, August 20, 2021 1:22 PM
To: main@ap-gto.groups.io <main@ap-gto.groups.io>
Subject: Re: [ap-gto] #APCC - V1.9 Tracking Error
 
Also, I suspect polar alignment isn't perfect. Could that be the cause.

The model can correct for that right? To what degree.

Is that polar az and polar Alt values in the model?


Rouz
 

Roland,

I'm not entirely sure.
The target moves "down" mostly with a 90 degree camera angle. 

I have solved the 1st and last image of the session.



First image
Observation start time ... 2021-08-20 09:16:09 UTC
Image center ............. RA: 20 11 56.941 Dec: +38 22 33.21

Last image:
Observation start time ... 2021-08-20 10:07:53 UTC
Image center ............. RA: 20 11 58.590 Dec: +38 22 21.79


Rouz
 

Ray,

I had it pointing at zenith (85 degrees) so having the mirror almost flat on the cell and the focuser hanging downwards.
Tightened each and every bolt in the setup too.

The mirror is bonded to the cell.
The focuser capacity is 25 lbs I have 8 lbs on it.

I doubt its flex as well.


Rouz
 

Bill,

Yes unguided with APCC corrections.

I doubt its PE as the image is consistently drifting in 1 direction. PE would cycle (sine wave like) around a certain point I believe.

It is neutral fine balanced as well.

I'm not sure about the polar alignment though. Could that be a cause?

Rouz,


 


Rouz
 

Model values


Rouz