Without the eSIF up (and I only just sent my money to Hans for the CD),
I can't confirm it, but I'm sure the Oly 500/8, like virtually all of
these, is a Maksutov-Cassegrain design with a spherical meniscus lens in
front holding the secondary mirror and sealing the lens, spherical
primary and secondary mirrors and a small lens group behind the primary
mirror similar to the rear groups on conventional tele lenses. Solid
cats are very rare.
I believe the reason these lenses don't have diaphrams has to do with
the mirror design. A diaphram before the primary mirror would be large,
heavy and expensive. Because of the folded light design, any diaphram
after the primary mirror reflection and before the hole in the primary
mirror would obscure the light to the primary mirror. By the time the
light is through the primary mirror hole, it is past the point where a
diaphram simply dims all of the image and into the area where it would
vignette or obscure the outer parts of the image.
Timpe, Jim wrote:
I'm quite certain the Zuiko is solid cat design. Don't know how they make
them so 'light' <g> pun pun pun
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