To: atm{at}shore.net
From: Steve Follett 
Reply-To: Steve Follett 


Hi all,

I have a theoretical question.

Since one can use a large flat to null test a Cassegrain telescope by
autocollimation, could one use the Wanieo null in the same way provided the
primary mirror was known to be good?

If I understand the Wanieo Null test properly (which I may not), the wave
front is essentially spherical as it comes off the primary mirror being
tested (assuming it's a good paraboloid).  Could that wavefront be used to
test the secondary in the same way one would use a Hindle sphere? Could one
null test the whole system this way?  Am I even picturing this correctly?

I am working on a Cassegrain telescope and I plan to test the primary using
a Wanieo Null.  It would be wonderful if I could test the whole system, or
failing that, the secondary using the same setup.

Steve Follett 

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