Re: ATM 11.2" F/2 Primary testing questions :)

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

With such a fast primary, the Foucault test will, indeed, be quite
inadequate.  Better to consider the null tests for a parabola along the
lines of the Waineo, Dall and other such tests.  These tests will mean that
you will need to be able to measure the full distances quite exactly but
since you're not trying to measure 10'  or more but rather less than 2'
where you can get accurate machinsts rulers then things are going to be a
lot easier to measure.
With that much difference in the ROC, you will be wanting to make the final
grinding at the 9micron to sort of match these numbers and it's going to be
fun getting the spherometer to measure them right as you are going to be
measuring a changing curvature.  Good luck!
That scope sounds to be a rather interesting one and I hope you are
successful in finishing it.  You will definitely gain a lot of knowledge of
how to test optics doing this.
Bob May
http://nav.to/bobmay
bobmay@nethere.com
NEW! http://bobmay.astronomy.net