I've been using a slightly modified version of the data reduction program that was published in S&T a few years back. My tester is a slitless design with a green LED light source. It is mounted on a milling machine (Lagun FTV3, weighs about 4000 lb.). With this setup I get results that are consistant to better than 1/10 wave by quite a bit.
I see quite a few mirrors because this is where most people in the Seattle club test them. I don't use a zone mask. The pin stick lets me see the whole mirror, which I feel is important. One more thing is that most of the mirrors are f/7 or longer.
So, can anybody with a good solid test setup and a little practice get results significantly better than 1/10 wave? Is the limitation based on experience or theory and calculation?
I'm not a real good observer, but the mirrors that have tested exceptionally well also are reported to perform better than most. What are others experiences and opinions about this?
Peter
-- Peter Hirtle notpete@scn.org Seattle, WA.