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tube rings/cradle/clamshell question...


RT65CB-SWL

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Hi everyone.

Hope this is the right place to ask!

A few weeks ago, I received a tip-off about a house clearance sale of some astronomy and photography equipment, via my astronomy society, I picked up and paid £5 for a used cradle/clamshell for my 're-modded' ETX105. Only problem, it is slightly over size.

I have decided to remove the Jubilee rings/hose clips the have secured the dovetail bar to the ETX [images below] for many years and use the cradle/clamshell and an existing dovetail bar. As the cradle is larger in diameter... I think it is from a 130mm OTA and the ETX105 is 124mm diameter. My question is: What material to use to pack it out for a snug fit. I have a 1m strip of 20mm x 10mm nitrile rubber. Will this be ok? or would some thick felt strip or cork strip be a better option? - tnx in adv.

IMG_0660.thumb.JPG.c0cda8510acd51b8dccf7f8596e13ace.JPGA5057402-94DE-4E35-A2DE-D8A6BDEFB67B.thumb.jpeg.2165097e2282e5347993d6249a14bd74.jpeg

 

BTW - I purchased/picked up a Meade DS-2102 [complete with cradle/clamshell attachment] from the same house sale/clearance earlier this week. 

Edited by Philip R
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  • RT65CB-SWL changed the title to tube rings/cradle/clamshell question...
  • 2 weeks later...

You’ve effectively got 3mm to fill, and I think you would want something fairly non compressible for perhaps 2mm of that, plus some felt up against the scope. If you have 3mm of foam then my concern would be that you have too much movement for it to be satisfactory. I guess you could over pack with foam and then compress it down, that may work well enough.

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I once "packed out" some over-sized SW rings for a 5" refractor years ago. I used a length of 2mm thick single-sided sticky foam strip and on top of that, a length of single-sided sticky felt strip. Width was approx 25mm and all available on Ebay. Worked a treat.

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