^- pardon the dopey "Office Memo" that my e-mail gateway inserts.
Hi,
I'm new to the list, but an experienced ATM. It's been quite a long time since I have done any mirror grinding though.
I have a 10" mirror with a beautiful rouge polish, which I perforated to within 1/16" of the front with a campbell's soup can attached to a bolt chucked in a drill press.
This mirror has been sitting on a shelf since 1983.
Though the polish is quite nice, the figure isn't. The outer 1" of the mirror is turned down severely. When I last worked on it, I spent many, many hours with all manner of special strokes, pitch lap pressed down by waxed paper on the outer edge, etc., to no avail. I just got the nice polish from all the time I spent on it.
I rather suspect that my problem is with the pitch lap. I had ground the mirror to a little less than f4, polished it poorly (my second mirror, in the impatience of my youth), aluminized it, reground it and repolished it. The tool is very thin, less than 1/2" on the edge.
I think that to start work on this again I should make a new polishing lap. What is the current thought on how I should do this. Do you think it matters, for example, whether the tool underneath the pitch has the same curvature as the mirror (so the pitch is of uniform thickness?). What materials should I make the tool from (dental plaster, cement, etc.?).
And any thoughts on getting rid of my edge?
I have the blank for making the cassegrain secondary. I'm not real sure how I will test the whole thing. Most likely borrow a flat from someone, maybe even make a flat.
Also, does the Eastbay Astronomical Society still have its workshops in Oakland, California on Friday evenings? I used to go there almost every week back in high school. I got a lot of help from, I think it was, Paul Zurakowski. I did complete a beautiful 8" mirror that I still use while I was going there.
Regards,
Mike Crawford Mike_Crawford@QuickMail.Apple.Com