Re: [ATM] hyperbola

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

With that size mirror, a subdiameter lap is the only way to go for hand
work.
The subdiameter laps make corrrecting large errors in the shape of a mirror
a lot easier than with a full sized lap.  If you are indeed overcorrrected
(i.e. a hyperbola) you want to mostly work the 70% zone area to bring the
curvature out to the edge which is low.
The problem with subdiameter laps is that you can easily do a zoned mirror
with them.  This is done by not blending the areas polished down well
enough.
Do make sure that if you are using a moving light source Foucault tester,
you indicate so in the software that you are using for data reduction or you
will be off by 2X one way or the other.
Bob May
bobmay@nethere.com
http://nav.to/bobmay
http://bobmay.astronomy.net

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