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CGEM loose when locked

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#1 garibaldi

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Posted 14 October 2012 - 03:31 PM

Had my orion 102 ed out last night on it's new CGEM mount which is brand new. I noticed when I when to focus the scope would shift a little from side to side. I think there is laxity in the declination gears or something. The clutches were locked tight and the scope could be shifted slightly, the image would go from side to side. When it was slewing and tracking I don't think anything moved though. Has anyone had this problem?

#2 dlpville

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Posted 14 October 2012 - 05:02 PM

There are a few threads on this forum for adjusting the DEC and RA worm backlash. It's an easy adjustment, and many of the Atlas/CGEM/EQ6 mounts need it, especially after a period of use.

Search for "CGEM DEC adjustment" on the "mounts" forum; you'll find it.
davel

#3 EFT

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Posted 15 October 2012 - 10:16 AM

I wouldn't call this a problem so much as a fact of life. What you are seeing is backlash between the worm and ring gear. You may be able to decrease it, but you generally cannot eliminate it without binding the gears. Here are some instructions for making the adjustment: Atlas-EQ6-CGEM Worm Spacing Adjustment. In general, shipping these mounts from one environment to another will result in the gears either tightening or loosening, so it is not uncommon that a little adjustment can be helpful. The key is to make very small adjustments and do it with the axis slewing so that you can hear when the gears start to bind.

#4 orlyandico

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Posted 15 October 2012 - 10:23 AM

Ed, is it possible to fit the gears tighter by lapping?

I tried lapping my Aeroquest worm with.. toothpaste and a drill. Had absolutely no effect.

#5 EFT

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Posted 15 October 2012 - 11:08 AM

Ed, is it possible to fit the gears tighter by lapping?

I tried lapping my Aeroquest worm with.. toothpaste and a drill. Had absolutely no effect.


It's possible, but not something I would recommend for most people to try because you can ruin the gears as well. Toothpaste is nowhere near agressive enough to do the job in any reasonable amount of time. I use a fine valve lapping compound and even that can sometimes take hours, not to mention having to take apart, clean, and put together the mount numerous times. After the lapping compound, then you can move to something like a polishing compound.

#6 Stew57

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Posted 15 October 2012 - 11:25 AM

Is the focuser smooth with no play? Sometimes there can be focus shift in the focuser.






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