Re: [ATM] Ultra-Thin Edge Support Idea - RE:[atm_free]ULTRA-THIN30"mirror from Hong Kong

["Nils Olof Carlin" <nilsolof.carlin@telia.com>]

> We have a great number of really smart and experienced people on this list
> so let's break the paradigm that thick mirrors are they only way to go and
> come up with a way to adequately support ultra thin mirrors? Observatory
> mirrors have thickness ratios which are radical in comparison to the 30:1
> just discussed. Surely with all of the potential on this board we can come
> up with a means to support large thin mirrors to an accuracy of 1/4
> wavefront.

Cleverness won't help against material physics, I suspect....
>
> - should be abandon lateral edge support and go with silicone attachment 
> of
> the mirror to the cell?

Counter-question: Are observatory mirrors siliconed?
What we need to ensure is that the support forces are evenly distributed. A 
"normal" floating cell does this in 2 dimensions for axial forces, but not 
in 1 dim for lateral forces - you don't know what will happen. This problem 
can be solved, I'm sure.

> - should we centrally support the mirror from the rear just like conicals 
> by
> gluing a rear support?

If you try to do that, supporting at a point behind the COG, the forces will 
bend the mirror.

> - should we use astatic cells?

Good question - I have no idea why that would be better than ordinary, 
balanced, floating cells. Anyone?

> - for super thin mirrors maybe we could built defection controls into the
> mirror support to improve image quality?
>
> I think it would be really cool if we as a group could identify the best
> approaches, perform experimental design on these ideas and examine the
> factors affecting success.
>
> The outcome of this work could set a new standard for amateur telescope
> making. This could be ground breaking work!

It's just that the pros have done a good deal of ground breaking work 
already. One might start by studying that. But the thinner, larger the 
mirror is, the harder to find a good support. And common sense (the kind 
that tells us that the Earth is flat at the center of the Universe) won't 
help much, I suspect.

N O 


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