Re: [ATM] Ball bearing for triangles,spherical aberration caused by thermal gradient in themirror:theresults...(long)

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

Bending the flat secondary will cause astigmatism.  If you already have
astigmatism, you can take some of that out with bending the secondary but it
isn't a good method of getting rid of the problem.  For one, putting the
mirror in at the wrong angle will make the problem worse.
The worst thing about bending the secondary is that it won't affect the
Spherical Aberration (SA) at all.  SA needs to be either figured out of the
mirror or a refractive corrector applied to the system.  SA is where the
edge focuses to a different point from the central area.  You don't fix it
by bending flats as you don't get the bending done correctly to fix such a
problem.
Bob May
bobmay@nethere.com
http://nav.to/bobmay
http://bobmay.astronomy.net

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