> a very experienced atm friend ... "tunes" out a
> bit of spherical abberation in his primary by heating the back side at
> a certain radius with a ring of resistors with a series reostat to control
> the power
Weird ! How big/thick the mirror was ? How large the zone ? Could it be detected by Ronchi in focus ? Was it Pyrex or plate glass ?
What was wrong with making the mirror good in the first place ? I'm not sure that I'd like ANY extra heat induced turbulence around my primary.
Bratislav