From: Ralph Seguin 
To: Tom Krajci , atm{at}shore.net
Reply-To: Ralph Seguin 


-+- Tom Krajci  wrote:
> I'd prefer that more people were involved in
> armchair research, rather
> than theorizing.  One starting point is the ATM
> archives at:
> http://astro.umsystem.edu/atm/
> (One of these days our email posts to this list
> will, hopefully, have added to them this URL.)

Here here.  Excellent suggestions.

That sure would be nice, along with the ATM swap list too...


> >...If this is the case then why not a million point
> > support in the form of say
> > short pile bristle carpet where each bristle will
> > only place an extremely
> > small pressure point before deforming to spread
> > the load further?
>
> You need to cool the back of the mirror.  Your
> proposal makes it difficult.

I'm not arguing for carpet here or against standard cells, but what about
using flex tubing with some sort of fluid (water?? :-) coolant?   Could be
woven into
the carpet, or just used in place of the carpet. I'm sure that tubing
probably has more than its fair share of problems that I am not seeing.

Seems to me that you really just want the mirror to be at thermal
equilibrium, and just slightly above the dewpoint temperature and well
supported.


> > Maybe that is where the complex engineering
> > solution could come into play
> > as the support for the carpet would also have to
> > be very flat and non
> > flexible so as not to allow the mirror to follow
> > said flex.....
>
> You are substituting one 'rather complex engineering
> solution' for
> another.   Can you show us how your proposal is
> simpler, or more
> accurate, easier to fabricate, or more likely to
> succeed?  That would make it more attractive.

That is a very useful corollary of Occam's Razor.

Please define "very flat".  I don't see the need for ultra flat
surfaces when you are using very flexible material like carpet.  You could
always make a full diameter optical flat for your support for your
carpet... :-)

Seriously, I'm not sure why using plate aluminum [insert your favorite
metal here] stock doesn't meet his criteria, as it is pretty flat stuff and
can be made as stiff as one desires (ribbing, thickness, ...) pretty
easily.

Thanks.
-Ralph




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