Re: ATM Concerning ronchi star test

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

Dave, excellent description of the test.  The only thing not stated is that
the lines are fuzzy edged lines rather than pure black and white lines that
the grating is.
The number of lines that cross the image of the star (Polaris is nice
because it doesn't move very fast across the sky and is bright enough for
the test) is what you will be seeing and if you get the grating at focus,
you will be able to see the shadows of the Foucault test run across the
disk.
FWIW, there is no optical surfaces in the eyepiece area as the defocused
image of the star is what the grating is obscuring when the test is being
done.
Bob May
http://nav.to/bobmay
bobmay@nethere.com
NEW! http://bobmay.astronomy.net