Re: [ATM] How fast is 150mm f/3.3 lensless Schmidt?

["Bob May" <rmay@nethere.com>]

Acrylic may be a better choice at that kind of F-ratio but there
is the problem of working 3ith the plastic.  First off, you don't
pour acrylic into a mold and wait for it to cure.  You pressure
mold it in a big machine at high pressure and a large diameter
piece of plastic like that means a big strong machine.  I've done
plastic injection molding so I am aware of those things.
The relaxation of the surface requirements are nice but still you
have to make the mold and you're not dealing with optical
machining here, but rather with  regular machinistts that
consider a thenth of a thousandth of an inch to be fine work -
and that doesn't include making ucrved surfaces!
I guess that if you get the two indices of refraction close
enough, you can probably allow for that much of a tolerance.
Bob May

rmay at nethere.com
http: slash /nav.to slash bobmay
http: slash /bobmay dot astronomy.net


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