Re: Re:ATM !! HELP!!! FIGURING HELP POLISHING!!!

["PETER JOHN SMITH" <pjifl@bigpond.com>]

Referring to the latest images (one Ronchi and a few Knife edge images) and
measurements on Geoff  Gallo's site, the mirror in question is progressing
in the right direction.

No Ronchi grating line spacings are given and I presume the pic. is taken
outside centre.  These are essentials which should always be specified. 
But the KE readings now give an interesting result.

Apart from a severe turned edge, the rest of the mirror is quite
reasonable.

At the moment, masking the 10 inch mirror down to 8.5 inch results in quite
a reasonable surface.  A little more masking and it is superb on the
figures provided.  Far better than most commercial 8 inch mirrors.  It
might be worth checking the readings to be sure.

OK, this amount of masking is depressing, but how many people produce a
superb 8 inch mirror first time around.

I suggest a strategy of planning and constructing the mounting of the
mirror while taking stock of the state of figuring.

Peter Smith.