Re: [ATM] Supporting thin mirrors for testing

[Ken Lowther <hermit@outofoptions.org>]

Quoting Mark Cowan <toolontop@yahoo.com>:




>
> The dowels are sleeved with heater hose to provide a
> non-slip support.  What I found fairly immediately and
> have had ample chance to verify is this:  if the
> mirror back is kept flush to the surface of the board
> and the mirror is slid down to make solid contact with
> the pads on the dowels (so there is no tilt
> available), astigmatism from the dreaded "potato
> chipping" effect disappears.  Completely.

How are the backs of the mirror prepared?  Banchard ground?  What kind 
of board
do you use that it is that flat?  Or am I reading too much in?  Is there good
contact between the mirror and board over the entire back and how do you
determine that?

Hermit, holed up in Youngstown, Ohio
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