[ATM] ?Glued Mirror Cell

[Thomas A Simmons <tasimmons@raytheon.com>]

Hey Jan and Rod,

  FWIW, I have a full thickness 12.5 inch mirror done up much as you
propose. It's bounced down dirt roads and such without coming out...yet.
So yes, it will work, and yes, you HAVE to be a genious (smile).

  What I did different than your proposal was to drill and countersink from
the backside of the bars, and then RTVd the screw to the bar. To tell you
the
truth, I'm not sure it was necessary. With proper prep of the mating
surfaces
and no gap save for a thin film of RTV, it just might work.

  Oh, one thing I did do wrong. With a forstner bit I drilled out a 1 by
1/8 inch
depression in the bar for the RTV to fill, which gave a roughly 1/4 inch
pad (total)
the thick pad allowed for the mirror to shift and therefore lose
collimation as
the tube rotated horizontal to verticle-

  If no-one gives you pictures, write me off line and I'll snap a
couple-it'll also
motivate me to get into the miror box for "just one more improvement on
that dang scope"

Date: Sun, 12 Sep 2004 16:15:20 -0700
From: "Jan and Rod Shea" <jnrshea@comcast.net>
Subject: [ATM] ?Glued Mirror Cell
To: <atm@atmlist.net>
Message-ID: <001901c4991e$62048af0$6401a8c0@NOTHALDESKTOP>
Content-Type: text/plain;            charset="Windows-1252"

I am designing what I hope to be a very portable lightweight 12.5" dob,
likely made from aluminum.  I'm willing to bite the bullet and glue the
mirror to the cell, and make a compliant hinge cell using RTV.  I am
thinking about a six point cell, PLOP derived, either Richard Schwartz
right angle style or conventional.  Would simply RTV'ing bars to the tops
of collimation bolts work, as long as the tops don't rotate when
collimated, and I used very wide topped bolts (? ~ 1") or machine screws?
Alternatively, some type of bearing could connect the glue pad and the
collimation bolt, but that kinda defeats the purpose...  Seems like the
glue should be GE type 840, about 1" in diameter, and 1/8" thick.  Has
anyone made a cell like this?  Can someone point me to pictures?

Thanks,

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