Re: ATM-mirror question

[Brian Nestel <blast@aloha.net>]

Howard.Banich@nike.com wrote:
> 
> Perhaps this falls under the category of silly questions, but what the
> heck, I'm curious and want to know:
> 
> - why are mirror testing racks and mirror cells in telescopes so different?
> Every test rack I've seen is made of wood and the mirror sits in it as
> casually as if leaned against a wall. Mirror cells, on the other hand, are
> carefully constructed metal affairs to insure no deformation of the carefully
> worked optical surface - that was tested on a wood rack.
Hi:
There is little deformation to most mirrors (depends on thickness &
size)
when sitting vertical in a testing rack, but when sittin sitting in a
poor mirror cell there is deformation from gravity depending on the 
position of the mirror in reference to local gravity.
-- 
Aloha   159 36 W, 21 58 45 N
Brian   Middle of the Pacific,
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