PPEC

[Don Waters]

https://openphdguiding.org/logs/dl/PHD2_logs_3HJw.zip

My earlier message may have gotten lost in previous thread.

I ran PPEC mode for the first time (as suggested) and got these results which seem to show a more pronounced PEC, so I am confused.

I do have the mount PEC ON, and I know that the general advice it to not run both, but I though the PPEC was designed to improve on the mount PEC.

The research I can find online suggests that I am getting something of a feedback loop from the PPEC over the mount PEC and suggests some changes to parameters.

Would appreciate your input.

Don

[Bruce Waddington]

You will probably get better results if you set the period length in the PPEC algorithm to 180 seconds rather than 480.  As far as using mount-based PEC, there's no way for us to know, it depends on the details of the PEC implementation in the firmware.  That will vary by mount manufacturer and even by mount model from the same manufacturer and none of that is public information.  If you want to get to the bottom of it, why can't you just run your own tests?  Run for 30 minutes with the mount PEC disabled, then 30 minutes with it enabled.  Repeat that several times to reduce the impact of unrelated other problems.  Do the back-back tests in the same part of the sky on the same night and eventually, on both sides of the pier.  Use the PHD2 LogViewer to analyze the results.

Good luck,

Bruce

[Don Waters]

Thanks, Bruce. I do plan to run the tests you suggest, but weather has been miserable here in Alabama. Summers are always hard, but this year, we have had rain/clouds for weeks at a stretch. I barely got that run in through thin, high clouds. And it really helps to have your insight.

Don

[Don Waters]

I was able to run 4 sessions: Mount PEC on, PPEC On; Mount PEC On, PPEC Off; Mount PEC Off, PPEC ON; Mount PEC Off, PPEC Off. The PEC and PPEC are definitely interfering. (AI explanation is that PEC produces a sine wave, and then PPEC creates a second, out of phase sine wave. When these two sine waves are added for total correction, they interfere, and at times can either be +/-.) Feeding the guiding log data into AI, AI suggested adjusting parameters for PPEC, but I prefer not to go that route. I also confirmed that my backlash is significant in this GGEM, making calibration more difficult and guiding as well. I had tried "resist" in declination and that was throwing everything off as pulses were not being implemented timely. (Should use N/S only.) Polar alignment is excellent.

So, I have ordered an Eq6 which reportedly has less backlash. The combo of long OTA, even with f6.3 and OAG, is challenging with CGEM. I know that the 9.25" is not the best choice, but I also have a Hyper Star to use with it for wide field.

Thanks for your help.

Don

[Brian Valente]

Don

We can't really offer much feedback without seeing your logs, if you were looking for that. 

AI doesn't really understand this domain: there are many mounts where PPEC and PEC interact just fine and others that are known to interfere with each other. It really boils down to the mount implementation of PEC. I don't expect feeding logs to AI is going to result in anything accurate. Hopefully over time that will improve 

Brian 

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Brian 

Brian Valente

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[Don Waters]

I understand that AI has its limitations and often gives wrong answers, but I find if I dig, I do learn more.

No, I did not expect more feedback. I was just confirming that with my configuration, I found PEC alone worked better that PEC and PPEC together.