Re: Re[2]: ATM Mylar windows

[andydtg@alpha1.phoenix.net]

Tom Stock wrote:
     
>     I was reading about mirrors made out of plexiglass type material which 
>     didn't work because of the expansion under temperature changes...but 
>     what about for an optical window??  It has a very very very long focal 
>     length (if any at all) so I would think that expansion would make 
>     little difference?

I use 1/8 or 3/16 Plexiglass for primary mirror dust covers. Occasionally I've
forgotten to remove the cover before using the scope - you wouldn't BELIEVE
what 2 passes thru this stuff does to the 'image'...

     
Andy Saulietis / DTG Alt-Az-Fp Drive Systems
12617 Harriet Ln
Santa Fe, TX 77510 USA
409-925-8854 Voice/Fax