Re: ATM Robo-Foucault, Image intensity, and Changing knife edge readings

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

Jim, was Carl's mirror coatee?  I've found a real problem with coated
mirrors on my test setup in that they overdrive the camera into the
autobrightness and that means that I've got to look at the comparison
between the left and right zones at a much brighter level.  When the
brightness gets down to the lower levels, the background of what a fully
blocked light starts affecting the readings which tends to pull the readings
closer to the center zone.
I have found that not only do you need to use a medium gray for the
comparison but the camera's output cannot be saturated or the results are
wrong for some zone.
Bob May
http://nav.to/bobmay
bobmay@nethere.com
NEW! http://bobmay.astronomy.net