ATM Tweaking Commercial Mirrors II

["Bennett, Thomas D" <thomas.d.bennett@lmco.com>]

I've decided to take the ATM plunge and try to refigure an awful 8" F4.5
commercial mirror that shows >1/2 wave under-correction and severe roughness
around its center. Would feel guilty about trying to sell it to someone and
wouldn't feel too bad if I botched it completely! A few questions about
trying to refigure a fast mirror like this: (1) Is the Foucault (have one of
these testers) test an adequate one for this mirror? I've seen where the
caustic test (don't have one of these testers) is recommended for faster
mirrors. (2) Sam Brown's book recommends using a medium soft pitch for
figuring - is this correct? (3) Tex's book specifies 3 different
parabolizing techniques: classical (zig-zag strokes with lots of overhang),
sub-sized tool, and accentuated pressure. Which technique is best for this
fast mirror? Tex said he couldn't parabolize an F4 mirror using the
classical method. (4) A local lumber sells wooden plywood disks in a variety
of sizes - can I use one of these as a cheap tool? Thanks for any help in
helping make my first real ATM experience an easier one. - Tom