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PEC calibration with an autoguider?

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#1 Lord Beowulf

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Posted 27 March 2009 - 08:58 PM

As it says, is it possible to perform the PEC calibration on a CGEM (or other Celestron GEM) using an autoguider? What can I say, I'm lazy and don't necessarily want to bend over my scope for the eight minutes required!

Thanks,

Beo

#2 LLEEGE

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Posted 27 March 2009 - 09:01 PM

Yes. In fact, you will get better results. Just start the guider, wait a few moments for it to settle in and then start the training run. Sit back, drink a beer and watch the guider do the work.

#3 jrcrilly

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Posted 27 March 2009 - 09:04 PM

Yes. In fact, you will get better results. Just start the guider, wait a few moments for it to settle in and then start the training run. Sit back, drink a beer and watch the guider do the work.


Sure thing - but first make sure you have a very good polar alignment and have the guiding set up for minimum errors. Any unneeded or incorrect guide commands will be stored along with the desired ones.

#4 Lord Beowulf

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Posted 27 March 2009 - 09:09 PM

Sounds great. Thanks! I'm just trying to get prepped and ready for whenever (if ever) my CGEM decides to show up. Of course I was reading the CGEM manual online trying to find the four-star alignment everyone talked about and finally found under the two-star alignment where you just keep adding stars...

Beo

#5 LLEEGE

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Posted 27 March 2009 - 09:14 PM

That is calibration, not aligning.

#6 LLEEGE

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Posted 27 March 2009 - 09:16 PM

And yes, you don't want to set the guider too aggressive. You don't want to chase the seeing. Slightly defocusing will help eliminate this.

#7 Lord Beowulf

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Posted 27 March 2009 - 09:22 PM

That is calibration, not aligning.


Sorry, I was just changing topics midstream. I was ready to post another question on "Where's the four-star alignment" after my original skim through the manual and search for "four star" turned up nothing in the PDF. However, I went back to see if it was something buried elsewhere under another topic and discovered that it's really a two-star alignment with extra stars.

Beo

#8 WadeH237

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Posted 27 March 2009 - 09:40 PM

Make sure that you download PECTool from Celestron. It will automate the process of collecting information from the guider and uploading it to the mount.

For best results, you should let the guider run with PECTool for at least 8 to 10 turns of the worm. This averages out the curve. I don't know what the worm period is on the CGEM (but PECTool should tell you.) On my CGE, it's 8 minutes - so it took me about 80 minutes of guiding to program PEC in my mount with a 10 run average.

-Wade

#9 alanon

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Posted 28 March 2009 - 12:20 AM

Do you have to retrain the PEC every time you move the mount?

#10 LLEEGE

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Posted 28 March 2009 - 10:38 AM

No. PE is a characteristic of the mounts mechanical imperfections. Once PEC is trained it will compensate for these imperfections. It is totally independent of the mounts setup and location.

#11 Alph

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Posted 28 March 2009 - 12:36 PM

Sounds great. Thanks! I'm just trying to get prepped and ready for whenever (if ever) my CGEM decides to show up.



Download PECTool from Celestron website and read about batch training.

#12 Tim C

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Posted 28 March 2009 - 02:17 PM

Can anyone share the results they have gotten using this method (i.e., before and after results)?

#13 WadeH237

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Posted 28 March 2009 - 08:31 PM

I don't have a CGEM, but using PECTool with an average of 10 turns of the worm on my CGE dropped PE from about 20 arc seconds peak to peak, to about 2 arc seconds peak to peak.

-Wade

#14 Tim C

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Posted 29 March 2009 - 10:46 AM

I don't have a CGEM, but using PECTool with an average of 10 turns of the worm on my CGE dropped PE from about 20 arc seconds peak to peak, to about 2 arc seconds peak to peak.

-Wade


That's pretty impressive. I plan to try it tonight if the clouds part. Seeing forecast is "bad" but if you average 8 or 10 cycles it shouldn't matter I wouldn't think.

#15 Joe Cipriano

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Posted 29 March 2009 - 09:38 PM

...Slightly defocusing will help eliminate this.


Only with a refractor. If your guidescope is a cat or newt, the defocused star image is a donut; IME AGs have trouble with those.

#16 alanon

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Posted 30 March 2009 - 02:32 AM

No. PE is a characteristic of the mounts mechanical imperfections. Once PEC is trained it will compensate for these imperfections. It is totally independent of the mounts setup and location.


Sorry I didn't get back to you sooner, but thanks for the info! It is good to know as I will have to travel and set up each and every time I use it. This makes one less thing to worry about for set up.

#17 waassaabee

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Posted 03 April 2009 - 08:53 AM

I don't have a CGEM, but using PECTool with an average of 10 turns of the worm on my CGE dropped PE from about 20 arc seconds peak to peak, to about 2 arc seconds peak to peak.

-Wade

Was this PECTool training done with an autoguider? That seems like the easiest and most consistent way to go.

#18 WadeH237

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Posted 04 April 2009 - 10:03 AM

Was this PECTool training done with an autoguider? That seems like the easiest and most consistent way to go.


Yes, it was. I just picked a star near the celestial equator that would not transit during the exercise, set up the autoguider and let it run for a bit to confirm I was getting solid guiding, then let PECTool record for about an hour and a half.

-Wade

#19 waassaabee

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Posted 04 April 2009 - 12:10 PM

I'll give that a try tonight! My ADD would never let me sit long enough to manually guide that long... :lol:

#20 LLEEGE

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Posted 04 April 2009 - 12:31 PM

...Slightly defocusing will help eliminate this.


Only with a refractor. If your guidescope is a cat or newt, the defocused star image is a donut; IME AGs have trouble with those.

Yeah, I guess I assumed the use of a small refractor for guiding is the norm, but some folks do use guide with other designs. Being a SFR, other designs don't get thought of. :grin:

#21 waassaabee

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Posted 05 April 2009 - 11:27 AM

Conditions precluded any PEC training last night, but a question did pop up in my little brain...

Seeing as how the PecTool is just monitoring an recording, and PHD is doing what it normally does, I'm guessing that one could image while all of this is going on, right? Not only am I lazy, but I hate to waste time that could be used roping photons...

#22 Tim C

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Posted 05 April 2009 - 02:30 PM

that's correct - you can image while recording the PE curve with PECTool.

#23 Doug6952

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Posted 10 April 2009 - 11:56 PM

Would it be better to do the PEC training with a long FL scope or a short FL?

#24 waassaabee

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Posted 11 April 2009 - 08:34 AM

Doug, Unless you have a mount that's not listed in your sig... The CG5 does not have PEC capability. :doah:

#25 Doug6952

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Posted 11 April 2009 - 09:17 AM

Doug, Unless you have a mount that's not listed in your sig... The CG5 does not have PEC capability. :doah:


I'm getting a CGEM at NEAF. So just getting myself prepared.






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