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Equipment Discussions >> Mounts

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Post Laureate

Reged: 01/14/13

Re: Dec Cogging on CG-5? new [Re: rmollise]
      #5845307 - 05/07/13 10:58 AM

I originally had my backlash compensation entirely off, but was having problems. I then turned backlash on to see if it would fix it. From what I saw last night, at the levels I had it, I clearly made things worse, not better.

At the time I originally put it in, my scope was badly out of balance. Now that my scope is balanced correctly, it is certainly worth turning it off and seeing what happens. Thanks Rod.

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Peter in Reno

Reged: 07/15/08

Loc: Reno, NV
Re: Dec Cogging on CG-5? new [Re: Madratter]
      #5845351 - 05/07/13 11:25 AM


Also, and possibly related, when calibrating with PHD, I get the movement along the N axis, but it fails to return very far at all doing the S calibration. Again, I thought that was being caused by weight balance issues, but that does not appear to be the case. I have tried up backlash settings to around 30, but that does not change things.

Increasing Max Dec Duration will help move the guide star in S direction during calibration. If you increase Max Dec Duration to 1500 - 2000msec, you should see the S movement during calibration. It may not move all the way back to original position but close. Turn off Dec backlash compensation in your hand controller. If you do not see S movement at all using large Max Dec Duration, then your mount may have issues.

Think of Max Dec Duration as a backlash compensation. Celestron mounts are notorious for excessive Dec backlash. My CPC0800 had it and increasing Max Dec Duration (1500msec in my case) helped quite a bit that I was able to guide up to 30 minutes per sub.

PHD's Calibration Step Size is depended on focal length of your scope. Don't use it to help reduce backlash during calibration. Increasing calibration step size too much can cause the guide star to jump out of guide camera's FOV and lose the guide star. Adjust calibration step size so that the total steps per direction is about between 12 and 20. The longer focal length of your scope the shorter the calibration step size.


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Post Laureate

Reged: 01/14/13

Re: Dec Cogging on CG-5? [Re: Peter in Reno]
      #5845564 - 05/07/13 01:15 PM

Thanks Peter. I'll give that a try and see what happens.

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