ATM Problems with 10"

[Balaji Ramani <balajir@paul.rutgers.edu>]

Hi,

I started working on my first 10" mirror.  I was aiming for a f/5.6.
During rough grinding, the overhang was too much and because of this, the
edge never got hogged out and this left a "outer ring".  After going
through Texereau's book, I started using the "approximately centered
strokes".  But before I could get rid of the ring, I ran out of #80 grit.
So, I just continued the same technique with #120.  Now I have two
problems.

1. Getting rid of the ring is becoming very difficult.  Any new techniques
to get rid of this ring?

2. The focal length is increasing.  How do I keep it at 5.6?

Clear skies,
Balaji