ATM First Ronchi test

[Andrew Melville <a.melville@mailbox.gu.edu.au>]

Hi

  Thanks again for all the help last week with the Foucault tester. I now have some images on my webpage. 

http://www.geocities.com/andrewjmelville/ATM/Figure/index.html

The images arent great but you can see that I have a turned down edge (photos taken outside focus). I tried the Foucault test first, and was a bit worried about the small distance (about 0.5 mm) between inside and outside focus. Now that I have had a look at the Ronchi test I think that it is because I have a nearly spherical surface. Does this sound right? I have only done 9 hours polishing so far and that with rouge, so it looks like I have a fair bit more to do. Would it be better to continue polishing with smaller strokes than 1/3 radius to try to remove the turned down edge? Or is this doing what Texereau predicts will happen if one tests too early, trying to alter polishing stroke and ending up with a "disastrous shape"? 


 Andrew J. Melville
 There are two kinds of people, 
those who test after polishing
and those who have a "disastrous surface"?