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Clamps/Straps for Mounting OTA to Edmunds GEM?

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#1 txmnjim

txmnjim

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Posted 15 June 2009 - 06:19 PM

Hi folks! I try hard to do searches and such to not have to
start new threads, but I can't find anything on this topic.
I am resurrecting and old Edmunds Scientific GEM (model B-2088)
and see that it was originally sold with clamps or bands that attached the OTA to it.
I have built a 10" OTA
out of Sonotube, and I am trying to figure out how to attach
it to the mount? I need someting that I can break down to transport,
but want something a little more sturdy than a belt strap ;-)
This little mount is quite sturdy and I'm hoping to do some astrophotography some day.
Thanks for any advice, or information on this topic!
Jim

#2 Exit-pupil

Exit-pupil

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Posted 15 June 2009 - 07:28 PM

Jim,

What I did was drill two holes through the tube and use bolts secured with nuts as semi-permanent studs. You can then slip the OTA onto the cradle and secure the ends of the studs with wing nuts. This will also keep it from sliding when pointed at the zenith, which might be a concern using straps.

Jono

#3 txmnjim

txmnjim

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Posted 15 June 2009 - 08:37 PM

This is a good idea. My tube is a 60" piece (nearly f8)
and was wondering if placement of these two anchor bolts
needed to be at balance point for the OTA? Particularly,
since I know next to nothing about GEM's, when balancing a
GEM do you need to have the OTA perfectly balanced as well?

Only other concern I have is since I'm using Sonotube, will
the weight of the "hanging OTA" rip out these anchor bolts over time? Thanks for the info.
Jim

#4 txmnjim

txmnjim

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Posted 17 June 2009 - 06:32 AM

Bump. Anyone have any ideas about balancing Newtonians on
a GEM? Or the possible strength of Sonotube? Thanks!
Jim






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