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From: BUNGE@osu-20.ircc.ohio-state.edu (Robert Bunge)
Newsgroups: sci.astro,sci.space.shuttle
Subject: Re: The end of Hubble
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Date: 23 Jul 90 15:53:48 GMT
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<Questions about the knife-edge test that amateurs use and HST>

The Foucault test - the knife-edge test that most amateurs use - is cheap and
easy under many conditions.  With HST is another question.  If I had access to
the clean room at PE when the mirror was tilted on it's side, I know I would
have tried to bring a small tester in and run some numbers on it.  However,
that's not to say that gravity might have mis-shapen the mirror to the point
that the test wouldn't have worked without special gear.  In theory, the 
Foucault test would show the errors involved without any trouble if:

1)The mirror was properly supported:
2)The error ARE all in the primary (the Foucault test doesn't like
convex secondary mirrors).

In some respects, the ATM's that I know are confused - not mad - as to why
a simple test like this wasn't done.

Bob Bunge
bunge@osu-20.ircc.ohio-state.edu