[ATM] fringe testing three flats

["Thomas Janstrom" <tomjan@ozemail.com.au>]

Hi All,

I'm most of the way through figuring a set of three 4.25" flats, now I'm
so far in that if I go with the bull's eye I get a not so even uniform
fringe that covers almost the entire surface area. Not real helpful! So
I've taken to pressing on one edge to de-center the bull's eye enough to
get more or less straight fringes across the disk, I usually aim for
about 10-15 fringes.

Anyway now that I'm down to an error of less than .5 of a fringe (bulk),
although there is a low center on one and another has a somewhat nasty
1/4W X 1/2" wide turned edge. So what I'd like to know is how do I
*know* if the surface is concave or convex? 

I've tried the moving my head towards and away thing as mentioned in ATM
vol. 1, but there is no discernable movement of the fringes one way or
the other. So any suggestions? 

Thanks......

Clear Skies, Thomas.
www.tjanstrom.com
www.norsewines.com.au 

 

-- 
No virus found in this outgoing message.
Checked by AVG Free Edition.
Version: 7.1.361 / Virus Database: 267.12.8/161 - Release Date:
3/11/2005
 

_______________________________________________
ATM mailing list http://www.atmlist.net/