From: "Bob May" 
To: "atmlist" 
Reply-To: "Bob May" 


The possibility always exists that you can indeed test with the Foucault
tester but I'd suggest that you learn how to do a full Caustic test (you
have to measure the traverse of the KE in addition to its longitudnal
measurement) as this will show the shape of the mirror better and more
accurately than the Foucault will.  I must be noted here that the Foucault
test gets harder to do as you go shorter while the Caustic test gets easier
to do.
If you are doing a convex surface, you will be best off doing a Hindle
test, especially for determining the strong hyperbolic surface that you
want. BTW, what do you need a strong surface like that for?  Concave would
indicate a small Cass scope but the e for those is a lot closer to 1 than 3
but a convex surface would be a decent secondary for a moderate sized
scope. Bob May
http://nav.to/bobmay
bobmay{at}nethere.com
NEW! http://bobmay.astronomy.net

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