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INDI Library v1.9.7 Released (29 Jul 2022)

Bi-monthly INDI Library released with new drivers and bug fixes.

Degenerate Mount models after polar align: How to improve?

  • Posts: 102
  • Thank you received: 21
After doing a polar align, I notice that the pointing model that is derived from that happens to be degenerate in (like) 60% of the time. Ok, what do I mean by that:

The PA process plate-solves three pictures around Polaris, that means the orientation of the celestial sphere in relation to mount coordinates is determined by three points, that all are next to each other. This means that the accuracy of the solution can diminish fast away from the pole and lead to large pointing errors.

Behaviour that I observed is that the first slew after PA is way off, then taking a new plate-solve (sync) does not fix it. You can even experience that the scope slews to below horizon after that solve or more than 120° away to your target. On one occasion, directions where inverted for DEC, but not for RA (or vice versa). I tried „Clear Model“ and newly solving, but did not work 100% of the time. „Best“ „fix“ so far has beento power cycle the mount and restart Kstars/Ekos. Then do a plate-solve (sync) in the vicinity of my target, which then usually gives dead on slew-to-targets.

Questions on understanding:
1) Are the PA solves used to built the pointing model or not? (My opinion: should not be used.)
2) What pointing model is there after PA?
3) Where is the pointing model (using EQmod with a AZ-EQ6 GT Pro)? Ekos? Driver/EQmod? In the mount?
4) What exactly happens on „Clear Model“ in mount tab?
5) Can I see the transformation function(s) somewhere? 

Question on how to mitigate:
7) What should the exact procedure be, to get an accurate pointing model? Please assume mobile use (PA necessary each time).
8 ) Would pointing, ca 5° off of Polaris during PA help to avoid that? 
9) If the pointing model is degenerate (as above), is there a way to avoid restarting Kstars/Ekos?

Thanks in advance, Jens (Grimaldi)

 
Last edit: 5 months 5 days ago by Grimaldi.
5 months 5 days ago #81151

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PAA is not use for pointing model. It's used to make sure you track correctly by making your mount axis aligned with the celestial pole. You need to use platesolving afterwards to improve your pointing model. Pointing model is in the driver, and when you clear it in the mount tab, all the sync points are removed from the driver.

Transformation functions are in the EQMod driver, or if you were using INDI Alignment Subsystem, then it depend on which Math plugin is activated at the time.
Jasem Mutlaq
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The following user(s) said Thank You: Grimaldi
5 months 5 days ago #81153

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