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Equipment Discussions >> Mounts

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gezak22
scholastic sledgehammer
*****

Reged: 08/15/04

Loc: On far side of moon. Send help...
AS-GT issues.
      #3906900 - 07/06/10 11:35 PM

Hi guys,

I have 2 small issues with my mount that I would like to get some feedback on.

1. Sometimes, when I release one of the direction buttons, the mount doesn't stop moving. This doesn't happen all the time, but when it does only one button is affected - N, I think. Any idea what's going here?

2. When calibrating PHD guiding, E and W calibration pass with flying colors. However, when looking at the motion of the star during the N-S steps, I notice that its motion is not perpendicular to the E-W motion. For example, W moves it left, E right (almost back to its original position), and N up. S will move the star up during the first two steps (a backlash issue I assume), then down with a significant 'left-right' component. ?

Other details: I use an Orion shorttube 80mm f/5 guidescope and I piggyback a DSLR with a 200mm lens. The setup is balanced. I always do a 2+4 alignment followed by an ASPA and then another 2+4 alignment. When I don't have issue number 1, the error after my alignment routine is ~1' per axis. Backlash is set to zero.

I forgot which firmware version I have, but it's the oldest one that supports the ASPS on the AS-GT.

Thanks for looking.


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seeker372011
scholastic sledgehammer


Reged: 03/05/04

Loc: Sydney , Australia
Re: AS-GT issues. new [Re: gezak22]
      #3907191 - 07/07/10 07:34 AM

I wish I knew the answer (Edit-well actuallY I suppose I do-the mount needs mechanical adjustment
I tried once but it doesnt seem to have worked so will need to give it a further tweak and see)
I have the exact same problem-in fact I am unable to autoguide in Dec anymore
this has started happening only recently though

Edited by seeker372011 (07/07/10 07:59 PM)


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Mike X.
scholastic sledgehammer


Reged: 06/28/10

Loc: Greece-Athens and Rome-Italy
Re: AS-GT issues. new [Re: seeker372011]
      #3908952 - 07/08/10 05:55 AM

It could be backlash or some play at the worm gear if the mount keeps moving for some time after the release of the button or doesnt moves for some time when you press the button.
In this case it could be adjusted with a simple regulation of the worm gear mesh.It's a simple operation and can be considered routine maintenance specially in mounts used for astrophotography.


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gezak22
scholastic sledgehammer
*****

Reged: 08/15/04

Loc: On far side of moon. Send help...
Re: AS-GT issues. new [Re: Mike X.]
      #3909508 - 07/08/10 12:43 PM

Quote:

It could be backlash or some play at the worm gear if the mount keeps moving for some time after the release of the button or doesnt moves for some time when you press the button.
In this case it could be adjusted with a simple regulation of the worm gear mesh.It's a simple operation and can be considered routine maintenance specially in mounts used for astrophotography.




Could you link a web page with pictures illustrating how to inspect the worm gears of the AS-GT? I've always wanted to inspect them, but never found a good guide.

Thanks.


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mikewayne3
professor emeritus


Reged: 02/02/09

Loc: San Diego CA
Re: AS-GT issues. new [Re: gezak22]
      #3911634 - 07/09/10 01:08 PM

I had the problem myself but now that I set the backlash RA to 01 and Dec to 01 that problem is gone (drifting after
I let go of the button that is)
Mike


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gezak22
scholastic sledgehammer
*****

Reged: 08/15/04

Loc: On far side of moon. Send help...
Re: AS-GT issues. new [Re: mikewayne3]
      #3911865 - 07/09/10 03:21 PM

Thanks, I'll give that a try.

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gezak22
scholastic sledgehammer
*****

Reged: 08/15/04

Loc: On far side of moon. Send help...
Re: AS-GT issues. new [Re: gezak22]
      #3987531 - 08/17/10 01:52 AM

Alright guys,

Sorry for resurrecting this thread. After disassembling the DEC shaft, relubing, and adjusting the worm gear mesh, problem 1 is no longer an issue but problem 2 is still present.

Any ideas would be appreciated.


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