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Astrophotography and Sketching >> Beginning and Intermediate Imaging

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Henry37
member


Reged: 12/05/09

Loc: Georgia
Guiding Problems
      #6120804 - 10/06/13 03:35 PM

I have been having guiding problems with my CGEM and PHD for a long time now. I haven't taken a decent image since 10/12. The problem is trailing stars. I have tried 3 different ways of polar alignment. ASPA, Photographic (CCD) alignment and PHD Alignment. Declination graph hardly moves. Problem is therefore in RA (RA Graph is not good). I tried with a 400mm Canon lens with not much improvement. I read somewhere that after a good polar alignment you should take an unguided 60 sec photo. If you still have traling it is most likely flexure. I can't do 60 sec with the 400mm. The mount has been Hypertuned. I have balnced and reblanced with no notable difference. I know to balance East heavy. I have even tried turning off Dec Guiding. no difference. Frustrated and looking for any ideas. I also want to add that PHD moves the RA in both East and West directions while guiding.

Edited by Henry37 (10/07/13 09:38 AM)


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nine44
sage
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Reged: 01/19/13

Re: Guiding Problems new [Re: Henry37]
      #6123780 - 10/07/13 11:05 PM

got any PHD graph screenshots?

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zerro1
Postmaster
*****

Reged: 08/02/09

Loc: Smokey Point , 48.12°N 122.25...
Re: Guiding Problems new [Re: nine44]
      #6123812 - 10/07/13 11:25 PM

Who Hypertuned it?
Have you contacted them?
What is the exposure duration of your guide camera set to in PHD?
1 second?
try 2 or 3 seconds?
Is it the same in all quadrants of the sky?

how many steps does PHD take to calibrate?

If your Dec graph is good then it's likely not a polar alignment issue.

Is the mount over correcting or is it not responding in a timely manor?(meaning is it continuing to track off target even though PHD is telling it to move the other way? )

a screen shot with the PHD settings would certainly help get reasoned responses...

It's possible that the worm adjustment is too tight or too loose. it doesn't take much adjustment to be too loose or tight


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CounterWeight
Postmaster
*****

Reged: 10/05/08

Loc: Palo alto, CA.
Re: Guiding Problems new [Re: zerro1]
      #6124338 - 10/08/13 08:49 AM

Henry can you post the PHD settings you are using and the gear you are using with? Also take a look for recent threads on this problem, there is one in particular that may be of benefit that is quite recent - often guiding issues can be fixed or greatly improved by changing the numbers in PHD and looking for changes in the graph and image results. As Warren mentions try using 2 second guide exposures and a step size of maybe 1800?

Also - how many steps is PHD taking in the RA and DEC to calibrate for you? A ballpark is to try and get the numbers in the 'brain' adjusted to where it is taking 12 or less steps to 'calibrate' - these can be watched in the very lowest PHD screen as it goes through the calibration process.


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Madratter
Postmaster


Reged: 01/14/13

Re: Guiding Problems new [Re: CounterWeight]
      #6124438 - 10/08/13 09:38 AM

From everything in the original description, it just sounds like normal periodic error to me. You are going to get guiding East and West with that, and unless you have a VERY expensive mount, you're stuck with it. That is what the guiding is for. The question isn't how many seconds you can go unguided. The question is what do things look like when you do guide? Is there still trailing? Is it East West in direction, North South, or some combination thereof?

East-West = Periodic Error
North-South = Declination Error
Some Combo = Either a combination of the above or flexure somewhere in the system.


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Henry37
member


Reged: 12/05/09

Loc: Georgia
Re: Guiding Problems new [Re: Madratter]
      #6125277 - 10/08/13 03:54 PM

I am sorry it took so long to reply. First I don't have any screen shots of PHD graph but wiil try tonight if possable. Ed Thomas Hypertuned the mount. I have not contacted him recently. The exposure duration is 2 seconds. PHD takes 10 steps to calibrate. The mount does correct in RA. The calibration step size is 2000. I hope I have answered your questions so far. It is supposed to be clear tonight so I will try to get photos of the graph and settings. Thanks to all for your suggestions.

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Henry37
member


Reged: 12/05/09

Loc: Georgia
Re: Guiding Problems new [Re: zerro1]
      #6125369 - 10/08/13 04:27 PM

I tried to adjust the RA gear clearence. Now the RA gets to a certain point and will not move. I tried giving it more and lass clearence but it still stops in the same position. I think I will call Ed Thomas.

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Henry37
member


Reged: 12/05/09

Loc: Georgia
Re: Guiding Problems new [Re: Henry37]
      #6125397 - 10/08/13 04:40 PM

Ed Thomas has agreed to take the mount back and see what went wrong. Thanks to all.

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Raginar
Postmaster
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Reged: 10/19/10

Loc: Rapid CIty, SD
Re: Guiding Problems new [Re: Henry37]
      #6125402 - 10/08/13 04:44 PM

First off, you don't want to guide at 1 or 2 seconds.. atmospheric seeing right? Henry, you basically 'fiddle' with that set screw until you can make it through the entire range of motion without it getting stuck. That usually means you have the 'best' meshing. After you play with it a bit, you'll get the sound of what 'good' is and what is 'bad' too.

What are the rest of your settings for PHD? My guess is that you're overly aggressive or not correcting enough. As it rocks back and forth, you're getting trailing... really not that surprising with new guys. Have you read this article?
http://www.cloudynights.com/item.php?item_id=2755

It really helps to understand what PHD is doing...


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rigel123
Postmaster
*****

Reged: 06/29/09

Loc: SW Ohio
Re: Guiding Problems new [Re: Raginar]
      #6125487 - 10/08/13 05:27 PM

Chris, why don't you want to guide at 1 or 2 seconds? That helps compensate for seeing, if you are shorter than that then seeing can play havoc with your guiding. Are you suggesting longer guide exposures?

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CounterWeight
Postmaster
*****

Reged: 10/05/08

Loc: Palo alto, CA.
Re: Guiding Problems new [Re: rigel123]
      #6125994 - 10/08/13 10:26 PM

I use 2 seconds for dialing in / getting close, works well - but there may be something specific to that mount?

That last symptom description - sending to Ed sounds like a good idea, top man and we're lucky to have him !


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Henry37
member


Reged: 12/05/09

Loc: Georgia
Re: Guiding Problems new [Re: Raginar]
      #6127715 - 10/09/13 07:30 PM Attachment (1 downloads)

Here are the PHD settings

Edited by Henry37 (10/10/13 03:37 PM)


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Henry37
member


Reged: 12/05/09

Loc: Georgia
Re: Guiding Problems new [Re: Henry37]
      #6127718 - 10/09/13 07:32 PM

Looks like I don't know how to enter a photo

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Madratter
Postmaster


Reged: 01/14/13

Re: Guiding Problems new [Re: Henry37]
      #6127861 - 10/09/13 08:52 PM

Just edit your reply and their will be a place to put it. You need to make sure it is no larger than 800x800 and must not be bigger than 200 kb.

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