6" lens
HOFFMAN@wmich.edu
Fri, 31 Mar 1995 10:20:27 -0400 (EDT)
IMHO -- making a 6" f/15 airspaced doublet is a classic
*LARGE* project. At a minimum, it is more than four times the
"glass-pushing" of making a 6" mirror, PLUS -- You have to get
the radii reasonably (within <1%) exact -- With a mirror, most
of us won't quibble over a couple inches in FL -- PLUS you have
to get the thickness correct -- PLUS you have to get the surfaces
concentric. Not really a good first project.
Also, you're right about the cost of the glass -- BK-7 and F-4
cost a LOT more than Pyrex.
And if you want to AR coat it -- that'll make aluminizing seem
CHEAP.
If you look in the back of Sky & Telescope you will see what
commercial optikers charge for a 6" doublet versus a 6" mirror --
theres a reason for the diffeerence.
Sorry to rain on your parade.
Richard Hoffman