Re: [ATM] 20" Fused Silica blank ( a bit long....)

[Dominic-Luc Webb <dlwebb@canit.se>]

On Thu, 28 Jun 2007, William Marriott wrote:

> interest.  And of course, the topics soon turned to
> what kind of scope to make out of it.

The really useful property of fused silica is its high transmission
across a lot of wavelengths relative glass normally used for making
primary mirrors. I do not think you will be able to actually take
advantage of the difference in thermal expansion. For the cost of
this piece, and now that it exists, I would first consider how it
could be applied for transmission. This piece is on the high end of
what can be used for a Schmidt corrector. I would consider a Schmidt
design with a 28" primary. The ability to cover the entire UBVRI
system on wide angle system with such large aperture would surely
impress a lot of people. You are a bit unique in having the possibility
for high transmission with a large aperture. A mirror does not seem to
me to be taking best advantage of this unique opportunity.

Dominic

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