Re: ATM update on foucault/interferometry difference

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

Just as a little not on the problems with RoboFoucault, I had a mirror that
I tried testing last weekend that I couldn't test.  The problem was that the
light level is apparently too high in the place that I am now forced to test
at (latest theory) and the two sides fail to properly match for brightness
of the zones.
The problem is that the side opposite the KE (slitless tester) tends to
gradually shade gray before the shadow starts to come across the mirror,
especially when testing the outer zones.  The shadow isn't related to the
light source not being able to reach that high of an angle as smaller
mirrors of nearly the same focal ratio don't exibit the problem.  In
addition, changes were temporarily made to "improve" the angle of irradiance
of the light source by putting several different diffusing screens between
the light source and the KE.  In addition, even the addition of a second
edge to produce a slit failed to make any difference.  The strangest thing
is that the dimming isn't of the same shape as the shadow movement across
the surface which is really the strange part but more like that the light
source isn't illuminating that part of the mirror anymore.
The wierd thing is that mirrors of the same focal ratio (most important for
the angle of the incoming rays) act differently.
Bob May
http://nav.to/bobmay
bobmay@nethere.com
NEW! http://bobmay.astronomy.net