Okay, I managed to determine the focal length by setting the lens in its cell on the picnic table outside and viewing a distant hill (about 1.5 miles away) with a 28mm RKE. This came out to 86". So, allowing for some focuser travel and 2" star diagonal backfocus, plus distance inside the support for the cell (that will be incorporated into the dewcap), I get a tube length of 78". A convenient length. I would rather err on the side of too short, because I didn't with my 6" f/10, and I can't use 2" star diagonals with it (until I cut it shorter, that is). I can always add a block behind the focuser to bring it out more if needed.
I'm going to start cutting a pattern for the baffles, then the baffles, then the tube slats for the nonagonal tube.
Speak now or forever hold your peace! (especially if you think I'm about to screw up!)
-Tim.
-------------------- "We`re just waiting looking skyward as the days come down.
Someone promised there`d be answers, if we stayed around."
-Orchestral Maneuvers in the Dark, "The Romance of the Telescope"
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Re: 6" f/15 Jaegers - OTAing this weekend!
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