Re: [ATM] Figuring help for Lutfu

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

A Foucault tester is easy to make.  The Stellafane site has a
nice design on theeir pages that is the basis for the ones that I
build.
The importnat thing with a tester is to be able to measure the
relativve distance measured to the mirror and be able to have it
hold the knife edge (KE) stable.  One fo the things this means is
that you don't put it on one rickety table and the mirror on
another!  The wobble as you move about will make for all kinds of
problems.  Test on the floor if nothing else.
As to doing the test, when you get the returned light from the
mirror to the right place, you'll see the light on the mirror
(you look at the mirror, not the KE!)  will dim and, as you slide
past the returned light, the light from the mirror will go out.
As you do this, you will  probably see that the light on't evenly
dim across the face of the mirror but rather do so in one area
first followed by other areas of the mirror.  Once you see the
results, you will probalby find that it is a really simpple test
to setup and run.
Bob May
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