1600GTO mechanical adjustments?

Mike Shade

I have some questions about mechanical adjustments on a first generation 1600GTO. I am having issues with the RA axis, specifically tracking. There seems a lot of periodic error that is hard to guide out. Stars are elongated in RA and I have large guiding errors in RA. This is guiding through the scope with an on camera chip. I have of course trained innumerable PEC curves and they seem to help for a bit and then not as much, hence want to make sure that I have the mechanical issues addressed before scampering off in other directions.

There is a Planewave CDK17 on the mount, maybe 120#OTA, plus camera, rotating focuser, and counterweights. Maybe 225# or more total. How tight do the clutches need to be on the mount? Permanent setup, used for imaging. What I have been doing is finger tight and about 1/3 turn past this but wonder if I am maybe getting some slippage as they are not tight enough. And, is it best to adjust this with the mount in PARK 3 (OTA north, counterweights down)?

There are two spring loaded plungers, accessible from the top of the RA/DEC motor housing. When the mount was recently greased, these came out. They were put back in how they came out and the bolt was tightened down. Question is, are these tightened snug, all the way or backed off a little bit? I had one of the red mounts years ago and they were all the way in and out a certain number of turns to set properly.

Is there anything in the gear train itself that can contribute to RA tracking errors? Anything to check? There was nothing obvious when greased.

In regards to setting gear mesh, set it as per manual except when tightening the bolts, will put fingers under the motor housing to lift ever so slightly and then tighten. I think George offered this for the first generation mounts. I tighten the left, center, and then right bolt then go back and snug in that order. Correct?

On my old 1200GTO, the thrush washer on the end of the worm comes loose and creates interesting problems and I have to go back in and tighten it up and put RTV on the threads to prevent this from backing off. Is this possible with the 1600s gear train?

Anything else to check here that I am missing? This is becoming a frustrating problem.

Mike J. Shade
Mike J. Shade Photography:

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