Re: [ATM] Testing Cassegrain Secondaries

[Richard <cnc@cncservo.co.uk>]

I would agree with David that a Null test of any form is the
most foolproof. My preferred form would be an Offner Null test
through the back of the mirror. It does involve using a glass
that has good optical qualities, but the two required lenses can
often be off the shelf items.

Another point that needs mentioning is to never ever rely on one
test. Test it at least twice, using at least two different
methods (cf HST...)

If you have access to an open well it can act as an excellent
auto-collimation mirror, but ask permission before polluting it
with an oil layer :)

-- 

Best regards,
 Richard



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