RA randomly over corrrects. see in guide log

[James Wentworth]

https://openphdguiding.org/logs/dl/PHD2_logs_9AYu.zip

Losmandy Gemini. Pec off

[Bruce Waddington]

You can use the PHD2 LogViewer tool to analyze these kinds of basic problems.  

https://openphdguiding.org/phd2-log-viewer/

https://openphdguiding.org/tutorial-analyzing-phd2-guiding-results/

The problems you're talking about in this log are mechanical, they aren't caused by guiding and they certainly aren't due to over-correction.  Here are the two biggest examples (RA in red):

Neither large excursion is triggered by a guide command that would push the mount west, which is the direction of the excursion.  As you can see, the guide commands (the red rectangles) were in the opposite direction as PHD2 tried to get the primary star back to its correct position.  This is probably caused by something in the payload that's riding on the mount - a cabling issue or a small shift in the guiding assembly.  The largest excursion we see here, about 17 arc-sec, corresponds to about a 20 micron unwanted movement of the guide camera sensor.  That's roughly 1/2 the thickness of a human hair.

You haven't given us any information about your overall setup or how you have it fitted out, but I would probably start by looking for tugging or binding cables.

Hope you can get it sorted out,

Bruce

[Brian Valente]

HI James

Any more detail here?

I don't see overcorrections. What I see is a couple places where something external to guiding caused a big jump in RA (and once in Dec). Guiding is reacting to this, not causing it:

also fwiw i suggest you switch RA algorithm to PPEC with a period of 239.3 seconds, disable auto adjust, and set your aggression to 0.8 for both reactive and predictive

On Sat, Aug 1, 2026 at 8:09 AM James Wentworth <jwentwo...@gmail.com> wrote:

https://openphdguiding.org/logs/dl/PHD2_logs_9AYu.zip

Losmandy Gemini. Pec off

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Brian Valente

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