Re: [ATM] figuring 10 inch mirror

["Bob May" <bobmay@nethere.com>]

The turned dege is the worst part of the surface as shown by Sixtests.  Go
and find out what the edge itself really is and you will find that it is a
fair bit longer radius than you think.  You need to do some fairly long
strokes to get the surface just inside of the edge down a bit.  I'd also
recommend that you don't repeat the exact same stroke length each time as
that may be part of the reason whay you have the ridge towards the middle.
Repetitive stroking tends to make for hills and valleys all over the place.
Also, keep rotating the mirror and the lap in opposite directions so that
each 2-3 strokes are in completely different directions and alignment of the
mirror to the lap.
By the time that yo get to the 1/10th wave area, you will be doing about 10
strokes to do a significant change in the numbers for the mirror's surface
shape.
Bob May
bobmay@nethere.com
http://nav.to/bobmay
http://bobmay.astronomy.net

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