Re: [ATM] Understanding Foucault

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

Yes, the excess light problem with the slitless tester is indeed a slight
problem in that new tester people forget that the light curve as the KE
obstructs the returned beam is highly nonlinear in the brighter range.  You
need to test the mirror somewhat darker than about half way as this point
ends up being the true midpoint of the light curve from bright to dark.  The
trap here is that if you go darker, the difference between zones of the
brightness that gets tested at tends to offset the KE position a bit.
Bob May
http://nav.to/bobmay
bobmay@nethere.com
NEW! http://bobmay.astronomy.net


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