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Old 26-01-2011, 08:51 PM
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peter_4059 (Peter)
Big Scopes are Cool

peter_4059 is offline
Join Date: Jun 2007
Location: Brisbane
Posts: 4,296
Originally Posted by erick View Post
My old Celestron C8 should have a 2" 24tpi thread. I have a GSO diagonal that fits, but two other GSO accessories (a straight-through 2" and a 2" Crayford focusser) that do not fit. All my reading suggests they are all nominally 2" 24tpi, but that thread tolerances were changed at some stage enough to cause this problem. My micrometer and thread gauge work suggests it is a thread depth problem. I am waiting to sit down with a machinist to work through all the threads, accuately measure them and see what we can adjust.
I'm certain it is 2" 24tpi however I've found there are machining differences in these threads depending on who has made them (ie GSO vs Orion) I assume this is a quality control issue rather than a difference in thread design.
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