Re: Valid Guide Rates for PEC on Gemini Level 4
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Hi Michael
Rene is the best person to answer this, but here are a few tidbits of my understanding
When you record PEC using a third party tool like PEMPro, the guide rate affects the speed at which corrections are applied (i'm not sure if it's in the capture, the playback, or both). First part is when you gather the data and then upload to the mount, Gemini needs to be at the same guide rate.?
Then when you're guiding, the guide rate needs to be at the same value as well. if you decide you want to guide at a different rate, you need to disable PEC or re-do it at the new rate. ?
for built-in PEC training, i'm not sure how much the above applies
On Mon, Aug 17, 2020 at 1:39 PM Michael Herman < mherman346@...> wrote: I always learn something new on this forum. I presently avoid needing PEC by the few improvements I made to the RA drive. That hot PE down to the 1 arcsec RMS (~2.4 arcsec Peak to Peak) range, typical of my area's seeing.? I do use autoguiding at 0.5x Sidereal rate to correct other errors like polar alignment error/drift.??
Earlier, I did use the Gemini-1 built in PEC training and built in PEC averaging .? It worked fine.??
However, from this thread, I really don't understand why the autoguide rate has anything at all to do with PEC training.? The autoguider is turned off during PEC data acquisition.? The "autoguide" camera is only used to "watch" the tracked star's RA position during sidereal tracking.? You could even be tracking the star with 2 or 3 second exposures.??
The PEC is fitted to the recorded unguided tracking data later, by either the Gemini built in software or the external PC software.??
So...can someone explain why "autoguide rate" has something to do with PEC??
Thanks, Michael
On Mon, Aug 17, 2020, 12:24 PM Brian Valente < bvalente@...> wrote: Update:
i found that reference in the documentation.
i checked with Ray, i think that may be out of date. the valid range is 0.2x - 0.8x
however, I really recommend you stick with 0.5x for two reasons
1. it's the best balance between slower speed (better for PEC) and faster speed (better for guiding)
2. there may be some parts of the code that are hard-coded to 0.5x. i don't know this for sure, i've only heard this in passing, so it may not be true. So the recommendation is 0.5x
also FYI if you change your guidespeed at any time, you will need to redo your PEC to match the guidespeed
Brian
I have always used 0.8x as the guide rate when training PEC on my G11 with Gemini 1 Level 4.? I was just looking at the Gemini instructions in PEMPro V3 and it has this warning:? The Gemini firmware only supports 0.3x and 0.5x guide rates - 0.5x is recommended.? This conflicts with the description of command ID 502, Guide Speed used for training PEC, in the Gemini Level 4 Users Manual.? That seems to indicate the full 0.2x, 0.5x, and 0.8x range is valid.? Which is it?
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Brian?
Brian Valente portfolio
-- Brian?
Brian Valente portfolio
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