Re: [ATM] All BK7

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

I missed one part of the spec.  I've got 200mm dia. glass for the
BSC1 and F2 glass which, of course, makes the design a bit more
difficult to do.  Unlike reflectors where the design can usually
be scaled up or down  without much care, refractors do tend to
blow up badly when sized up as Richard knows.
Good try with the Schupmann tho, Richard!  I'll note that it
really doesn't matter what type of glass you have so long as the
two refractive parts of it are from the same melt of glass.  This
little strange requirement also applies to the Houghton lenses
for that matter.  With the Schupmann, I suspect that if the
glasses are close enough to eachother, you can possibly tune out
the color error but with the Houghton, the color error may still
persist.
For a Schupmann, I'd probably do one with the reallly cheap K5
glass.  Anybody for a forty inch or larger Schupmann?  Make the
biggest refractor in the world and get excellent color correction
to boot.
Bob May
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