Re: Re[2]: [ATM] Use of bearings in (static) mirror cells

["Olivier Biot" <olivier.biot@versateladsl.be>]

Hi Richard,

As far as I can remember from previous posts (dating back from the end of 
the 90s), this "lateral" RTV joint may become a major cause of astigmatism 
as it will induce compression to the mirror edge, for example when the 
mirror compresses and expands due to thermal expansion.

However, Jerry's last message is interesting. Imagine you glue your mirror 
to a well-balanced mirror cell, AND provide adequate lateral support (with 
e.g., less than .5mm (1/50 inch) clearance), that would considerably reduce 
the "shear tension deformation" induced by the mirror's weight in 
non-vertical aiming, as you'd considerably reduce (almost "eliminate") 
lateral motion.

It is then important to position the lateral supports at the same "plane" in 
which the mirror's centre of gravity is located. This way you avoid unneeded 
"momentum" for the forces which compensate eachother.

What's your idea regarding this approach?

Best regards,

Olivier
----- Original Message ----- 
From: Richard


> Hi Jerry,
>
> Has anybody tried a compliant edge support, such as a short
> section of tube fixed to the telescope, say 10mm bigger radius
> than the mirror, with that 10mm gap filled all round with a high
> compliance silicone RTV ?. I can't think of a more gentle edge
> support which both spreads the load and is fairly easy and cheap
> to build. 


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