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CG-5 mount / drive jitter issue

Started by m87, 11/24/2003 03:24PM
Posted 11/24/2003 03:24PM Opening Post
Past weekend I was comparing with two 4" refractors
side-by-side at high power, one on a GP mount and the
other on a CG-5 mount. After a while I noticed the
image from the CG-5 mounted scope was slightly
unstable -- it seemed to wander or jitter just
slightly -- maybe <1 arcsecond amplitude and
and several oscillations per second. Normally
I would have attributed this to "seeing" but
the jitter was most definitly NOT there in the
GP mounted scope ten feet away. (Seeing was
superb BTW.)

Anyone else seen this sort of thing in a CG-5?
One thought I had, was whether the stepper drive was
exciting some resonance in the mount. Does anyone
know the drive rate on these (steps per second)
or whether it is different from the GP mount?
When the CG-5 RA drive is going I can hear a 1-2 Hz
ticking sound; is that the step rate (seems too
coarse?) or something else? I suppose it could
also be an issue with rigidity of the CG-5, but
the capacity, etc. seems similar to the GP.

Thanks in advance for any help....
Posted 11/24/2003 07:21PM #1
My experience with these sorts of mounts is that the problem can be the tripod, it is just not stiff enough.

Make sure that all the bolts and screws on the tripod is as tight as possible and that the legs are not extended any more than necessary.

Try turning off the drives while looking at a close double at high power and seeing if this smooths things out.

Jon Isaacs