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Sliding CF tube in rings

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#1 KShank

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Posted 03 November 2012 - 01:30 PM

Hey
Ok I have swapped my ota on my VMC260 from the original metal tube to a very nice CF one. First the setup. The ota is set in two parallax rings, with Losmandy plates top and bottom. The rings are on 23" plates, with about 1" not supported on the ota. Whole thing is on an AP1200 mount in an observatory.
Problem: now the Ota slides in the rings. Sure I can tighten the ring, but I can feel the CFdeflect, and that affects collimating. Did I mention that collimating on this scope has to be razor right? Anyway any thoughts on how to keep its table in the rings without deforming the tube? Perhaps as simple as placing some material on the felt on the inside of the rings that "grip" CF better?

I have quite a bit of weight on the tail piece, so slippage is a pain when shooting narrowband and using a piggyback scope. Before this swap, I was able to track well enough with a very well mounted Borg 50mm & rgh to go 20' subs at native fl on the 260. Now I'm at 5'.

Ideas most appreciated
Keith

#2 Peter in Reno

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Posted 03 November 2012 - 02:07 PM

I had similar issues with my C-8 EdgeHD and Parallax rings. The OTA was also slipping and I contacted Parallax and they sent me extra felts. They said to add felts on top of existing felts to bottom half of the rings.

Contact Parallax and they respond very quickly.

Peter

#3 EFT

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Posted 04 November 2012 - 11:38 AM

Definitely need to add more cushioning material to the rings. It could be more felt or you could try something like craft foam that would have a little more gripping power.

Where did you get the CF tube from?

#4 LouHalikman

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Posted 04 November 2012 - 06:24 PM

Stick-on felt pads for furniture work great. My 80 APO is carbon fiber and would not hold in the rings without the felt pads. Lou






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