Re: [ATM] Mirror support question

[<atm@hudler.org>]

Mark,

	I was looking to modify a 24 inch in just the same fashion. The idea
came when I saw the whiffletree support drawings for the Keck primary. Just
turn radial support inside out and replace the diaphragm with simple o-rings
(or mercury ring seals) set into a groove on the radial support. 
	The point of the o-ring is to allow for tip/tilt and axial movement
while minimizing de-centering and CFE issues. You can do the same thing with
a thin width of Teflon that's just pressed into a groove of the same width.

 	Having seen nasty pictures of chipped and broken mirrors we were not
going to allow the radial support to project no more than halfway up the
central hole. This makes it impossible to pinch the inside edge of the
mirror causing it chip followed of course by a litany of foul language. 
	To prevent the mirror from falling out just place a single clip
somewhere close to the mirror edge. The mirror only has to move the gap to
the clip before it becomes bound between the clip and support.

	Looking at almost all SCT's you will find the same type of support;
only in our case it's strictly radial.

	If you're baffling, look at threading the inside of the tube and
using that to screw your baffle into.

Jack


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