Re[2]: [ATM] A model of the Hindle Sphere test of a convex Hyperboloid

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

Hi Kevin,

Saturday, April 2, 2005, 5:50:02 PM, you wrote:

KW> You have a 1 micron tolerance, or so it seems.

Not wishing to be pedantic Kevin, but 0.01mm is 10 microns. It's
a shame how many imperial/metric conversion/unfamiliarity errors
I see on this list, when it's so easy to just take an hour out
to learn metric once and for all. If NASA guys had done it then
we'd know more about Mars than we do... (This is a general rant,
not aimed at you!)

Did you see the message on Offner Null testing of convex mirrors
I posted a month or so back?. There's a good section on it in
Geary's "Introduction to Lens Design" (Willmann-Bell) and I
found it fairly simple to optimise an Ofnner null setup for my
hyperberloid secondary, looking 'through' the mirror so the
reflecting suface under test appears concave. Although this
requires a decent homogenous optical glass for the mirror, the
test setup uses two standard lens, one PCX and one BCX, although
I fancy a precision grade of lens is required. Post the R, K and
D of your mirror here and I'll see if I can adapt my
prescription for it.

-- 

Best regards,
 Richard



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