Re: [ATM] ronchi pics digital camera etc

[Mark Holm <mdholm@telerama.com>]

jeff newsom wrote:
> As well , I've seen pics of foucault testers employing some type of  eyepiece for magnifying direct viewing . What might they be using?   Thanks ---Jeff Newsom

I think this is probably a small telescope used to magnify the image of
the mirror.  This is an old trick, but not old and bad.  In fact, it is
pretty clever.  The scope goes just behind the knife edge, where your
eyeball would normally go.  The scope is focused on the mirror, just
like your eye is in the usual Foucault setup.  A small finder scope may
work well if it has enough focus out travel to bring the mirror into
focus.  People have even used the finder from a Tasco scope for this
purpose.  It is about the only useful thing I have ever heard of being
done with a Tasco finder.

Mark Holm
mdholm@telerama.com

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