Re: ATM Has anyone worked with membrane mirrors?

[astillma@nit.AirTouch.COM (Anthony Stillman)]

In Ed Mannely's book Unusual Telescopes an absolutly brillint idea using a vacumn
and electric field is presented for the construction of large membrane mirrors. 
A number of the dificulties are discussed as well as a ronchi of a mirror.

I've thought about making one my self, but haven't gotten to it.  I have a number
of ideas I've throght through and would love to start a thread.

First there is the issue of changing pressure in front of the film
This could be delt with by sealing the tube perhaps with another membrane and
working the whole aperatus above atmospheric.

Second, there is the issue of irregular streaching in the membrane.  My uncle, 
for a while, manufactured film for capacitors.  It had extrodinary uniformity.
This might deal with a great deal of the streaching issue.

Third, reflectivity is a problem.  Both due to the thin coatings usually applied
and the the streaching and de-streaching breaking up the coating layer.  I think
some experiement is warrented here.  Keep in mind though that a very very big 
primary could be built.

Please, anyone interested, chime in.  I think there is potential here.

Anthony