Re: ATM Horrible figure!

[Anthony Stillman <atmer@flash.net>]

>...have turned the mirror EXACTLY 1/4 of a turn every time

This could be the problem.  It is important to randomize how much you turn
and NOT line up any part of the stroke.  It is difficult for a human to
keep everything turning and maintain a pattern sufficient to introduce
astigmatism, but it is possible.  As you thought, your best bet is to
return to a sphere.  You might try to accomplish this with the polishing
tool, but you may need to return to fine grinding.

Recently a glass pusher at the workshop, having attached stops on his
polishing board to control his otherwise longer than 1/3 stroke, discovered
he had created a ring zone about 1/3 in from the edge.  Remember, machine
like repetition will be punshed and of course the floggings will continue
until you are finished.

Anthony