Re: [ATM] cylindrical mirror grinding

["Bob May" <bobmay@nethere.com>]

Jess, making mirrors of any size to odd shapes is really a fairly difficult
chore, both to make and then to test.  Elliptical surfaces can be tested by
the two focal points method but parabolas and hyperbolas both need to be
tested with either nulling optics or with the Foucault test although
interfrometery can handle much of this.
Grinding and polishing such surfaces is often done with restrained rotation
of the tools and mirror and can become rather interesting to get the right
curvatures in each direction.  Jose Sassian (don't remember whether it was
one or two "s" at the moment) had an article about doing a secondary for a
scope of his about 10 or more years ago.
The professional community complains enough when they have to do a parabola
so trying to do a parabola in one direction and a hyperbola in the other
direction will really drive the cost up.
Bob May
bobmay@nethere.com
http://nav.to/bobmay
http://bobmay.astronomy.net

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