[ATM] Pesky oblate spheroid, Seeking advice polishing an 8" F/6

[Mike Lockwood <melockwo@uiuc.edu>]

Dave, Kirk,

You both have the same problem, an oblate sphere or "dinner plate". 
Hope my short web page on the subject will clear things up:

http://bi-staff.beckman.uiuc.edu/~melockwo/mirror_making/oblate/oblate.html

This cure works for me and has worked for my mirror making students. 
It's just a subtle change in polishing technique.  Try this simple 
change before pouring a new lap, etc.

	Mike Lockwood


Kirk Brown wrote:
> My mirror surface is looking pretty good except for the raised
> center that starts about 1/3 in from the edge. My mirror is
> polished out and has been for quite awhile. Is it possible that my
> polishing style is causing the raised center because it's too
> "robotic." How can I fix this? Larger strokes or figure-8s? Thanks!

davidtrumble@comcast.net wrote:
> Hi all,
> A small group of us in Boulder started mirror making about a year
 > ago. A few of us are now in the middle of polishing.
> Mine looks like ...
 > http://www.atmlist.net/contrib/davidtrumble-at-comcast-dot-net/
 > 02-02-06%20Alan%20Dave/Dave3.jpg
> (Knife edge on the left.)
> I'd like to hear what people think of this "dinner plate", and how
 > to best proceed from  here.
> I using a dental stone tool with Gugolz Pitch #64, formed with a
 > PitchLaps.com mold.
> -- David Trumble Boulder, CO 

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