Re: [ATM] Foucault imaging fast mirrors?

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

Dominic, sorry that I'm a bit late with this reply but I am
trying to catch up with te old stuff, responding to the neweer
stuff.
Use a lens to reimage the KE at the edge of the Canon's lens.
The focal length will probably be fairly small to handle the
light cone.  You don't need an achromatic len ns, just a sinlet
as the focus doesn't need to be that accurate.
Don't forget to insure that the return beam is close to thesource
otherwise the astigmatism will be huge and you will see it badly
in the images.
If yo're doing a sphere, the foucault test will work but if
youu're going to do something else, a wire or caustic test will
definitely be better.  You may als prefer to try one of the null
testsjust so that you don't have to do measurements at various
radii.
FWIW, I've measured my F1.95 sphere and found that hard enough.
Yours will be a fair bit more difficult!
Bob May
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