Double achromats for Orthoman

[Greg Erker <erker@xxxxxxxxxxxxxx>]

 I was playing around with my Edmund
Scientific 36mm dia by 82mm FL lenses
last night. I tried them together
as a double achromat and they work
very nicely.

  The magnification is about 10% more
than my Red Button viewer (44mm FL lenses)
so I'd estimate the double achromat FL
at about 40mm (probably 41 if it's 82/2).

  With the two curved faces facing each
other there was no pincushion distortion
I noticed (was viewing a slide not a grid
though).

  With the slide side lens flipped around
(curved to slide) then there was pincushion.
[this is the config that the Surplus Shed
36x92's work best in].

  Coverage was good. With my glasses on
I could see all but the very corners of
a 7 perf (albion) mounted slide. My two
lenses are mounted in the white PVC holders
that Mark made for me so the slide side one
has its clear aperture reduced by a mm or two
on the slide facing face. Coverage improved
when I flipped the slide side lens over since
the clear aperture at the rounded face is
the full diameter of the lens.

  So with proper lens mounting I think 7p
would be fully visible even with glasses.
Without glasses you might be able to see
almost 8 p (don't know for sure).

  When I bought these lenses 2 years ago
I paid $35 each. They are grade 2 coated
experimenter grade lenses. My latest catalog
shows a part with same dia and FL with the
same part number except that the first letter
has been changed. The price on these is $26.20.
I don't know for sure if these are the same
lens as mine or if EdSci's part numbers are based
on the lens dia and FL and the different letter
means it's different.

  Disclaimer: if you are considering spending
a hundred dollars to try this out you might
want to borrow my lenses first to check that
you like them.

Greg