Re: [ATM] RE: Best webcam/ccd for Foucaultgrams?

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

I use one of those giant red LEDs for a finder for my tester.  The LED just
throws out a good strong light beam to the mirror and is reflected back to
another part of the tester where I put a penned in box for a target for the
return beram..Just align the tester like you normally do and then turn on
the finder LED and draw the box where the beam returns and you will be able
to return back to that position everytime that you go to setup the tester.
You can even tell the focus point with this setup.
Slits are not hard to do as they are merely two blades opposite each other.
Please note that the width of the slit mostly does nothing bu linearize the
upper range of the brightness of the returned beam.  Thus, the real width of
the slit is not all that important for the Foucault test but does have a
little bit of a particular width (less than 1 line pair is needed) for the
Ronchi test.
Bob May
bobmay@nethere.com
http://nav.to/bobmay
http://bobmay.astronomy.net

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