From: "mlbrown{at}everstrive.com" 
To: atm{at}shore.net
Reply-To: "mlbrown{at}everstrive.com" 


Kerry,
 Post your Foucault measurements and the dimensions of your mask zones.
This group is excellent at giving advice from this data.  You *may* have an
excellent mirror with a hole in the middle right where the secondary
shadows it.  Chances are you don't, but the measurements will tell us a
lot.

If your surface appears nice and smooth, going from where you are to a
parabola is not a bad plan.  I agree with Scotty that it is very easy to
blow right past a parabola -- in my last mirror I did that several times
before I learned to take measurements more often (and switched to rouge,
which works slower).  I actually spent less time getting there than I did
erasing my mistakes.

Note that if you do have just a central hole, the area you want to work
down is NOT the extreme edge, but somewhere between the center and the
edge.  Draw a profile of the shape that your mirror is currently at.  Now
draw a paraboloidal surface that is tangent to your current shape in the
center and intersects the mirror at the outer edge.  This will show you
that the glass you want to remove is mostly in the middle.

=Matt



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