Feature tracking AZ GTi

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festoon
Posts: 20
Joined: Fri Jan 18, 2019 9:52 am

Feature tracking AZ GTi

Post by festoon » Wed May 27, 2020 4:57 pm

Hi Robin,
I've been trying unsuccessfully to get feature tracking working with my mount (AZ GTi in AltAz mode). I thought I'd please ask for your (or the community) help to resolve.
Firstly, I can control the mount fine using the SynScanMobile Telescope ASCOM driver.
Whenever I try to use the Feature Tracking function using a field of stars I do not get past calibration. I have tried to follow the suggestions you give in your documentation but still cannot resolve the problem. (I'm doing EAA observing at a focal length of 412mm and hoping to track objects using the feature).
Attached is the log files for the calibration - hopefully that will help identify if anything is really wrong.
Log_2020-04-04T21_09_00-10060.log
(798.42 KiB) Downloaded 17 times
Log_2020-04-04T21_09_00-10060.log
(798.42 KiB) Downloaded 17 times
If you require any more info please do let me know.
Best regards,
Colin
Attachments
GuidingLog_2020-04-04T22_21_44-10060.log
(34.36 KiB) Downloaded 7 times

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admin
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Re: Feature tracking AZ GTi

Post by admin » Wed May 27, 2020 7:43 pm

Hi,

I think the fundamental problem here is that the feature tracking was never really meant to track a field of stars – it's aimed at tracking lunar or solar images where there is a detail on the surface that it can identify and follow. I'm actually quite surprised that its managing to have what looks like a decent attempt at calibrating based on the star field.

Looking at the calibration data in the log files, it seems that the movement in the image is proportionally much faster when the mount is moved in the X positive direction compared to when it is moved in the X negative direction – for instance it takes an X movement of 6.5 to move about 40 pixels in the positive direction an X movement of 24 to move about 50 pixels in the negative direction. This is enough to make SharpCap abandon the attempt to calibrate since it expects the movement speed to be the same in both directions. I wonder if the problem here is either if your mount is not tracking, or if perhaps every time SharpCap asks it to move it pauses tracking briefly meaning that every move request will lead to a certain amount of drift in a consistent direction.

Cheers, Robin

festoon
Posts: 20
Joined: Fri Jan 18, 2019 9:52 am

Re: Feature tracking AZ GTi

Post by festoon » Wed May 27, 2020 9:21 pm

Thanks Robin,
The mount was tracking before I initiated the calibration for feature tracking. And the drift idea is an interesting one. I wonder if there is any way of testing which/what the issue is?

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Re: Feature tracking AZ GTi

Post by admin » Thu May 28, 2020 6:08 pm

Hi,

The simplest thing would just be to watch the screen as SharpCap is moving the mount around – SharpCap requests the same movement rate in each direction, but may be the mount is urging to do that. It should be fairly obvious from the rate at which the stars drift in the image – if that is not roughly the same in both directions then SharpCap is not going to be accepting the calibration is good.

Cheers, Robin

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