Re: [ATM] Fkex Mirror.

["Bob May" <bobmay@nethere.com>]

More consider something like a 3" or so piece of glass for this
job.
The problem is that the larger pieces of glass would represent
more of the side of a parabola if you use it directly.  With the
flat as a director, this, of course, doesn't apply.  You do run
into the problem tho of getting a really good flat for the flat
as any errors there will be significant relative to the focal
length of the scope.
I made a 40' FL surface on a 10" piece of glass and found that
I'm going to have to make a flat with a minor axis of that
otherwise the solar scope idea won't work - the difference in
sagittal vs tangential focus ends up being about 6' when the sun
is about 45 degrees above the horizion!
I did see a probably 2" sun scope one year up at RTMC and the
focal length was pretty long, probably about 150' or so (from the
fence to the trees across the soccer field by the lake) and the
image was somewhat faint but quite visoble and of decent focus
that you could see a fair bit on the sun.
Bob May
bobmay at nethere.com
http: slash /nav.to slash bobmay
http: slash /bobmay dot astronomy.net
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