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Eric,

The issue with PEMPRO is not the difference between East and West moves, but I don't want to get off topic.

At the time you were using PEMPro there was an issue introduced when adding the two-cyle PEC programming for the Gemini, but that has been long since fixed.

Hopefully someone else can measure their residual PE/drift at different guide rates using the same PEC curve
so we have more than one sample.

PEMPro has been able to program the Gemini controllers since 2005, so I've seen hundreds of curves where drift was introduced by using the wrong guide rate.

Hopefully a few people will report if the amount of drift changes depending on guide rate. It could well be that the latest firmware has changed the behavior.

That said, the amount of drift change when changing guide-rate will depend on the PEC curve. The lower the periodic error of the mount, the less drift will be introduced when changing guide rate. So, one arc-sec/minute could be right for your mount and a small change in guide rate. It could be a lot more under different circumstances.

-Ray Gralak
Author of APCC (Astro-Physics Command Center):
Author of PEMPro V3:
Author of Astro-Physics V2 ASCOM Driver:

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Cyclone
Sent: Tuesday, August 18, 2020 8:25 AM
To: [email protected]
Subject: Re: [Losmandy_users_io] Valid Guide Rates for PEC on Gemini Level 4

Ray,

You seemed pretty stubborn about me being wrong about the move distances being different between
East/West

The issue with PEMPRO is not the difference between East and West moves, but I don't want to get off topic.



According to your PDF when you had mismatched guide and PEC rates you observed drift.

The report does not say that. The mount reports its state as slewing periodically and momentarily, but there is
no change in drift. I assume that because the PEC divisors are different than the guide divisors, the mount
reports its state as slewing at each PEC correction, but there does not seem to be any other side effect.



Have you tried measuring drift with mismatched guide/pec rates?

I did measure the drift with the same PEC curve and different guide rates and the drift in RA does not change
(approximately 1 arcsec/min).

Hopefully someone else can measure their residual PE/drift at different guide rates using the same PEC curve
so we have more than one sample.


Eric