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More results with CPC1100 and Pempro

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#1 astrovienna

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Posted 02 May 2010 - 08:46 AM

After seeing Psyire's post on this subject, I decided to try Pempro on my CPC1100. The bottom line is that I reduced my PE from about 33 arcsecs to 5, so hopefully I can get better guiding results now. This is the pre-PEC data. You'll see it also shows one wild RA excursion. Unlike Psyire, I have not been brave enough to swap out my CPC11's plastic ball bearings for steel ones, so that may explain this. I edited that out of the data before preparing the PEC curve.

Kevin

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#2 astrovienna

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Posted 02 May 2010 - 08:48 AM

And here is the comparison of the pre-PEC and post-PEC curves.

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#3 Psyire

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Posted 02 May 2010 - 05:51 PM

Kevin, that is awesome! You'll be pleasantly surprised when you go to image next and reap the benefits.

#4 astrovienna

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Posted 02 May 2010 - 06:43 PM

I hope so. I spent most of four nights doing this! But they were pretty worthless for imaging, anyway. Moonlight, low transparncy and poor seeing.

BTW, what do you make of the excursion shown in the first graph? I saw others, too. Ray Gralak suggested maybe a bit of debris in the gears. Since the scope is only six months old - and has spent much of that time at Celestron, in fact - I kind of doubt the ball bearings are an issue, but I don't really know.

Kevin

#5 Patrick

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Posted 03 May 2010 - 12:07 AM

Hi Kevin,

Could you explain the PEC procedure you used to create the post PEC curves? Is it the same procedure described in the Celestron manual, where you have to guide the scope for 8 minutes? If you have to guide to get this PEC profile, how does PEC really help you? Wouldn't this be the same as autoguiding for each session?

Patrick

#6 astrovienna

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Posted 03 May 2010 - 06:06 AM

Pempro simply measures the position of the star recorded by your camera. It doesn't guide or anything. You just start it up, then let it run as long as you want (or as long as your polar alignment can keep the star in the camera's field of view). Then it analyzes the data to figure out your PE, and creates a curve to cancel out your PE that you can then upload to the mount. Run Pempro again, this time with PEC on, and let it generate a new "curve," although this one is really just a measure of your tracking errors, not PE.

It would be interesting to compare this to results with Celestron's PEC Tool. Running PEC Tool in batch mode, your autoguider keeps the star in view. PEC Tool records the commands sent to the mount, then creates a curve and uploads it to the mount.

Kevin

#7 Patrick

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Posted 03 May 2010 - 10:51 AM

Okay...I'm with you now. So, Pempro replaces the native Celestron PEC routine? (My incorrect assumption was that Pempro was just recording the PE, not creating a PEC program). How would you use Pempro during an actual imaging session then? Would you normally run Pempro plus autoguiding? Does Pempro know where the mount gears are after the power has been shut down or do you need to run a new PEC routine each time?

Edit: I'm reading through the Pempro manual, so some of my questions are being addressed there. If you have any comments beyond that, I'd be interested in hearing them!

Thanks,

Patrick

#8 astrovienna

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Posted 03 May 2010 - 03:01 PM

You can't really image while recording data for Pempro. Or autoguide, as far as I know, although there is some implication in the manual that you can. Pempro uploads the PEC curve to the mount, where it stays. So you don't need to run Pempro after that, just turn on your PEC through the hand control.

Kevin

#9 Psyire

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Posted 03 May 2010 - 11:41 PM

Yeah, it's really quite simple.

Step 1: Analyze your Mount's Periodic Error (PE) with PEMPro.

Step 2: Create a PE Curve with Pempro based on the above analysis.

Step 3: Upload the PE Curve to your mount via. PEMPro.

Step 4: On your next imaging session be sure to turn on your mount's Periodic Error Correction (PEC) with the Hand Control before you start autoguiding. This will take a lot of duty off your autoguider and result in much better tracking/guiding.






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