Re: [ATM] Mirror cell design

[Guy Brandenburg <gfbrandenburg@yahoo.com>]

Might I point out that in the olden days, epoxy glues
and RTV cements had not yet been invented?
Though I don't hear of anybody trying Leon Foucault's
1859 innovation, of having a little inflatable rubber
bladder sitting underneath the [thin] mirror, which
the observer can either blow a bit more air into, or
else let a bit more air out of, as conditions warrant.
You have the tube long enough so that you can blow in,
or let out, the air while you are at the eyepiece.
Sounds like something worth trying, to me.
Guy Brandenburg

--- Jeff Anderson-Lee <jonah@cs.berkeley.edu> wrote:
> [Sigh.]  Yes Richard, gluing works well for standard
> thickness or even 
> "thin" mirrors, but reportedly has problems near the
> horizon with 
> ultra-thin mirrors.
> 
> Jeff
> 
> Richard Schwartz wrote:
> 
> >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.
> >
> >. . . Richard
> >
> >  
> >
> >>[Original Message]
> >>From: Jeff Anderson-Lee <jonah@cs.berkeley.edu>
> >>To: AMT Mailinglist <atm@atmlist.net>
> >>Date: 7/20/2004 8:30:56 AM
> >>Subject: Re: [ATM] Mirror cell design
> >>
> >>Wouter van Reeven wrote:
> >>
> >>    
> >>
> >>>So, is there an alternative to using slings? I
> suppose creating a ring
> >>>around the mirror would not leave enough room for
> the mirror to expand
> >>>under heat, right? How about putting a rubber
> ring inside a metal ring?
> >>>Wouldn't that give enough support and not too
> much friction
> >>>
> >>>      
> >>>
> >>A rubber ring would add an incredible amount of
> friction. You could try 
> >>wrapping the mirror with a few wraps of teflon
> plumber's tape perhaps.
> >>
> >>Jeff
> >>
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> >>
> >
> >
> >
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=====
Guy  Brandenburg
Washington, DC
My home page:
http://home.earthlink.net/~gfbranden/GFB_Home_Page.html
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