Re[2]: [ATM] On Axis Foucault

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

Hi aplanatic,

Tuesday, June 14, 2005, 5:43:37 PM, you wrote:
 
aac> I've made several f/2 and faster spherical mirrors
aac> for Schmidt cameras, a collimator and a concentric Schmidt
aac> Cassegrain.  Once you get used to judging Foucault shadows
aac> across a wide field of view, I don't think you'll have any
aac> problem testing the reference mirror.

That's encouraging. Would a microscope eyepiece or objective be
of any use behind the KE?. Also, does a Ronchi grid offer any
advantage?
 
aac> If you need an f/2 reference mirror be sure to
aac> oversize it.  It's always the last 3-5 mm at the edge
aac> that's so hard to get right.

Yes, I've got plenty to spare with an F/2 reference mirror. I'm
unlikely to ever need to test anything faster than an F/2 mirror
at its COC, so an F/4 beam will cover it.

aac> Don't stick anything through your pelicule.  The
aac> results of such an experiment are quite disappointing.
 
Ouch. I destroyed one more subtly by breathing a tiny drop of
saliva onto it. Pellicles are hygoscopic...

-- 

Best regards,
  Richard in the UK



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