2 months ago PHD stopped accurately guiding

[rwhite]

2 months ago PHD2 stopped accurately guiding. Have been unable to run 3 minute subs on a AVX mount.  Have tried calibrating PHD2 several times with no success.  Attached is link to my last PHD2 files

https://openphdguiding.org/logs/dl/PHD2_logs_2gRK.zip

[wave...@talktalk.net]

Hi rywh...., i'm still learning myself, so what I see in the logs is subject to expert confirmation. Anyway, I think there's probably a lot of backlash in the Dec drive and maybe a loose joint or cable drag, which are having an impact on your results. You haven't mentioned measuring the backlash, so the first thing I would do is to run the Guiding Assistant for two or three worm cycles to assess the Baseline performance of the mount. There's information on that in the  documentation highlighted at the top of the main page. This will provide a lot of basic data about how the mount performs unguided and what it may require to get you on a better path - polar alignment error, Dec backlsh issues, min moves, etc. With that info available, i'm sure you'll receive more focused advice from the experts.

Cheers,

- Jack

[mj.w...@gmail.com]

Many basic errors in your setup and technique:

https://openphdguiding.org/phd2-best-practices/

Michael

Wiltshire UK

[bw_msgboard]

Here are some comments based on what's in the log:

 

1.  Don't try to calibrate at or near the pole.  Calibrate close to Dec=0.  When you get a good calibration, keep using it, don't keep doing it over and over, just calibrate at the start of each night.

2.  Don't use LowPass2 for your Dec algorithm.  Your setup has numerous mechanical problems and isn't nearly stable enough to use that algorithm.  You should revert all the guiding parameters to their default values - your problems are with the gear, not PHD2.

3.  Your mount has a lot of reversal delay (backlash) and probably too much resistance (stiction) in Dec.  If you increase the mount guide speed to 1x sidereal (or close to it), the situation will improve somewhat but you will probably need to also make mechanical adjustments.

4.  There are sometimes large, abrupt guide star excursions that push the Dec axis into instability.  These are not caused by guiding, they are probably caused by something moving around in your guiding assembly.

 

 

 

Dec is in green here.  At the point this large excursion started (arrow), the Dec motor wasn't running at all.  If you reposition your scope to point at Dec=60:00:00 and RA=03:00:00, do a careful inspection of the whole guiding assembly - scope, mounting points, cables - to see if anything can pull or move around. It only has to move by about 15 microns, about 1/3 of the thickness of a human hair.  That's a consequence of the tiny pixels in your guide camera and the finder-scope you're using for guiding.  Also make sure that the scope is well-balanced in Dec with the clutches tight.

 

Good luck,

Bruce

 

---

From: 'rwhite' via Open PHD Guiding [mailto:open-phd...@googlegroups.com]
Sent: Tuesday, January 11, 2022 8:21 AM
To: Open PHD Guiding
Subject: [open-phd-guiding] 2 months ago PHD stopped accurately guiding

2 months ago PHD2 stopped accurately guiding. Have been unable to run 3 minute subs on a AVX mount.  Have tried calibrating PHD2 several times with no success.  Attached is link to my last PHD2 files

https://openphdguiding.org/logs/dl/PHD2_logs_2gRK.zip

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[Richard White]

Thanks Jack for the suggestions.

Guiding assistant and cable runs makes a lot of sense.

Will let you know how it works out.

Richard White

Sent from my iPhone

On Jan 11, 2022, at 12:05 PM, 'wave...@talktalk.net' via Open PHD Guiding <open-phd...@googlegroups.com> wrote:



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[Richard White]

Thanks Bruce

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