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CGEM 8/3 gear issue solution coming?

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#1 petemumbower

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Posted 18 November 2012 - 02:07 PM

Word from over on the Celestron Beta testing site is that they are working on a solution for the 2.667 issue that makes PEC very ineffective. Sounds like they are shooting for first half of 2013 to release this fix.

It will be interesting to see how they implement this fix. From what I understand, it is in the the gearbox attached to the motor. So hopefully they will offer a replacement gearbox.

#2 orlyandico

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Posted 18 November 2012 - 04:18 PM

I always thought it was a software-only fix...

#3 petemumbower

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Posted 18 November 2012 - 08:01 PM

The underlying issue is the gearbox. From my understanding and being on the PEMPRO forum, the 2.667 is just not repeatable with regularity for software(PEC) to address it. Unless I am missing something?

#4 Starhawk

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Posted 19 November 2012 - 12:20 AM

It would be correctable if your loop time was long enough. It should be possible to break our the different constituents. I tend to doubt they want people doing 90 minute PEC correction training runs.

-Rich

#5 Stew57

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Posted 19 November 2012 - 08:48 AM

Actually a 3 worm rotation PEC would take care of it. My 8/3 error is repeatable but not easily guided. I would like to see a motor/gearbox change but don't see that coming. A firmware solution fix would be fine by me and unexpected.

#6 freestar8n

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Posted 19 November 2012 - 04:42 PM

Well there has been a form of solution for this issue for many years now, and that's to use MetaGuide to correct for the one term preemptively.

The thing is - I was interested in guiding out PE terms several years ago, which is why I added this feature - but I realized that it didn't help much as long as you just guide tightly in the first place - because the errors from the longer period terms will be small in each correction.

It's not clear to me if people actually have a problem guiding in RA due to this 8/3 term or not. If they did it would show as oblong stars in RA and smaller in Dec - and even then it could be due to faster gearbox terms or other factors. But if the stars don't tend to be stretched in RA, I don't think reducing this term would help much.

But if anyone is interested in trying the preemptive correction stuff in MG I'd be happy to help give it a try. You just enter the period in seconds, begin guiding, and in a short time it should display the phase and amplitude of the term as it gathers data - with no need for a training session or an added switch in the gearbox.

Frank

#7 petemumbower

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Posted 19 November 2012 - 06:16 PM

Frank, that does sound like an interesting solution. I started using MetaGuide for collimating, but had interest in trying the guiding out with it. The only device I have that works with MetaGuide currently is my PGR FleaMV camera. I am not sure if it would be sensitive enough. Also, I currently use a 80mm ShortTube for guiding with my SSAG. I do not have an OAG either. So would this still work with what I got?

#8 freestar8n

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Posted 19 November 2012 - 06:29 PM

Hi-

As it happens I will very shortly have a new release out that has better support for Flea cameras. I'm not sure which Flea camera you have but the normal mono ccd Flea's are very sensitive and well suited to guiding. The cmos and/or color may not be as good though.

But either way - for a proof of concept you can try MG guiding on a bright star and see if your results are better in terms of RA error.

The 80mm scope should be fine for guiding and the only issue is flexure - which you would have anyway. So that also isn't different witn MG.

I haven't worked much with the frequency locking stuff in MG lately, but it should work. You will know it is working if you see the amplitude and phase lock in as it tracks the star and zeros in on the frequency of interest. It would be easy to test the basic idea without even imaging - just guiding on a bright star.

So I would be happy to help you give it a try and I would be interested in the results myself, out of curiosity. I recommend waiting I think just a few days for the new release since it has many other enhancements.

Thanks,
Frank

#9 petemumbower

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Posted 19 November 2012 - 06:41 PM

Frank,

I have the FireFly MV...it uses the a mono CMOS (Micron MR9V022 chip). But it seemed to do well with faint stars while collimating. I look forward to trying this out and waiting a few days is fine, looks like I have clouds to deal with here in Michigan this week.






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