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GSO Primary adjusting screw size?

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3 replies to this topic

#1 tag1260

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Posted 05 January 2013 - 02:08 PM

Anyone know the size of the adjusting screws on the primary on an older GSO scope? How about the locking screws? I know the secondaries are 3mm.
Thanks

#2 acochran

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Posted 05 January 2013 - 02:32 PM

Replaced the primary collimation screws on my Lightbridge 16" Dob (Made by GSO???) with longer ones. They were 8-125mm I think. Take one to hardware store that sells metric screws and check, Ace in my town.

#3 Patrik Iver

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Posted 06 January 2013 - 12:59 PM

Hi!

They are metric M7 on my 2005 vintage 12" GSO dob. A very unusual size almost never found anywhere. The locking screws are M6. I made my own by having a 8 mm stainless rod threaded M7 at one end and M8 at the other end. Then I locked a M8 thumb-nut (locktite) to the 8 mm end. The unthreaded 8 mm section gives nice and "slop-less" operation and it just fits the holes in the rear casting.

The Farpoint Astro website sells two different knob sets with 2008 as a year when the size changed, but does not say what the difference is. Telescope Service (in Germany) defines their Farpoint knobs as size M6. My guess (pure guess - no firm info) is that pre 2008 the size was M7, and 2008 and onwards M6.

#4 tag1260

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Posted 06 January 2013 - 06:19 PM

Thanks for the replies. I guess the thing to do is to get a set of Bob' Knobs for it. The 8mm are too big so I would guess that they're 7mm.


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