Re: ATM Ultra-Ultra Short Focal Length Mirror

[Aplanatic@aol.com]

Hi Eric:

> My father, who makes a living from industrial salvage auctions, recently
>  showed me a mirror he obtained. He told me it came from a machine used for
>  silicon microchip lithography. It is a fused silica mirror with a diameter
>  of about 10 inches and a focal length of about 5 (yes FIVE) inches. It is
>  mounted in some sort of really fancy stainless/monel/inconel mounting ring
>  and is about three inches thick. He ask me if he could use it in a 
telescope
>  (he had seen my dobsonian and thought he could use it for one of his own).

Well, assuming it's a sphere, you could make an f/1 Schmidt camera 
out of it.  You would then have to learn the black art of Schmidt 
corrector making.  In thinking about, I would can this plan.  An 
f/1 Schmidt corrector is no fun at all.

Or, again assuming it's a sphere, you could bore a hole in the center 
and use it as a Hindle Sphere for testing convex mirrors.

I"ve Foucault tested f/0.5 spherical surfaces, it's not easy but it can
be done.

Dave Rowe.