Re: Polishing Woes
Tony Cecce, Corning, NY (CECCE_AJ@corning.com)
Fri, 28 Apr 1995 10:27:50 -0500 (EST)
I am just about finished with polishing my first mirror, a 5.5 inch.
I had a central depresion so I used tool on top most of the time and
the edge actually polished out first. I was also using polishing pads
instead of pitch. It took me about 5 hours to get a complete polish,
but I think I could probably do it now in about two hours. I managed
to almost eliminate the hole but the the pads did give me some other
zonal errors and I wasted another hour trying to work them out before
going to pitch. I went to pitch and put about 30 minutes of polishing
in last night. The zonal defects are much "softer" now, kind of looks
like the zonal defects are melting away. Needless to say, my outlook
on life has improved dramatically since I finally have a sphere in sight.
BTW, I occasionally get waves of shadows travelling across the mirror
during focault testing. I assume these are due to air currents.
Where is the most likely place for the air currents to be occurring,
at the mirror surface, the knife edge, or inbetween? These seem to
occur at random and will definately make the task of getting readings
impossible so I will take any suggestion on how to address this problem.
I built the tester ala berry and am using the spare bulb from my mini-mag
so I do have a major heat source 1/2" below the knife edge.
Tony