RE: [ATM] Mirror cell design

["mbyorick" <mbyorick@starband.net>]

Yeh, Richard, I glued (RTV-ed) my 16" mirror to its cell, completely
dispensing with the original mirror clips and nylon edge-retaining pins,
only to find to my horror that the cell-induced astigmatism disappeared
as a result.  And since we all know we can't trust RTV to hold the
mirror in place, I have a helper stand next to the mirror at all times
during observing, to catch the mirror when it decides to take its
inevitable plunge to the ground.  For similar reasons, when touring
modern observatories, I never walk underneath the 20 ton mirrors that
are RTV-ed to their cells, as you never know when they might come
crashing down.  

-Mike Byorick
SW New Mexico

-----Original Message-----
From: atm-bounces@atmlist.net [mailto:atm-bounces@atmlist.net] On Behalf
Of Richard Schwartz
Sent: Tuesday, July 20, 2004 8:24 PM
To: Jeff Anderson-Lee; AMT Mailinglist
Subject: Re: [ATM] Mirror cell design

The most popular alternative to a sling is to use metal clips at the
edge
of the mirror to retain it in the cell.   If you screw those clips tight
enough, friction will prevent the glass from sliding around or rattling
in
the cell during transport, and your scope will always be perfectly
colimated.

Whatever you do, you do not want to search the ATM list archives for any
discussion of this.   Some crazy radicals advocate GLUING THE MIRROR
INTO
THE CELL.   If that were a good idea, the optical great masters of the
1930's (such as John Hindle) would have discovered and used that method.

Any fool can see that if you glue the glass into the mirror cell it will
be
under a lot of stress when the temperature changes and the figure will
be
ruined.


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