Bruce: 40 feet doesn't sound right to me, but my only reference is Suitter and he is looking at Newtonians. and he is doing more than just collimation. Perhaps, just for collimation you don't actually need to come to focus. Just centering the blob will suffice. DT
________________________________ From: Bruce Hugo <bruce.hugo@yahoo.com> To: "utah-astronomy@mailman.xmission.com" <utah-astronomy@mailman.xmission.com> Sent: Sunday, February 9, 2014 9:25 PM Subject: Re: [Utah-astronomy] Not enough backfocus
Hahahha! Yes, probably a really good thing it is not on his window! Instead of the artificial star, it would be a full moon! ROFL!
I installed some Bob's Knobs on the Meade LX200GPS 12" and was going to use the Hubble 5-star artificial star generator for collimation. I did the calculation as to how far away to place it. About 40 feet. So I measured to a tree in the back yard from my home office window. 58 feet. The telescope is set up in that room. Unfortunately... the scope does not focus that close. In fact, about the closest I can focus is my neighbor's back fence about 200 feet away. Guess I'll have to ask him if I can set the Hubble on his fence one of these nights. Hahahaa!
Better on his fence than on his window... :)
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