P3D sharp viewing lens

[Peter Abrahams <telscope@xxxxxxxxxx>]

The cost of a pair of ocular lenses with really excellent optics would be
considerable.  Not because the optics are unusually sophisticated or
non-standard, but because of the economies of scale.  The most comparable
consumer product would be a loupe sold to look at photo negatives.  These
usually have aspheric lenses, which are much more difficult to make than
spherical lenses, and are outrageously priced, good ones can be $150
(though it is a challenge to magnify by 5 times or so, an entire 35mm
negative with very low aberrations).   But there are binoculars that sell
for under $200 that use aspheric lenses in each ocular; and $50. telescope
eyepieces are every bit as sophisticated.

Eric's test of racking in & out of focus & examining the edges is a great
test for field curvature.  Why was this aberration overlooked by some
users?  Because a truly flat field view is completely unnatural, our normal
vision is sharp in the middle of the field & quite blurry at the edges.
Looking through a flat field binocular is a very unnatural view, but once
you've seen it, you can see what you're missing with inexpensive binoculars
(though some users don't like it).  Try one of the top of the line
binoculars (up to one thousand dollars or more), by Nikon, Leitz, Zeiss, or
Swarovski.  You can also take your stereo viewer to a camera store &
compare it with one of the best magnifiers sold for viewing negatives, the
difference should be apparent.

Ye Olde Red Button is the best of the readily available (more or less)
stereo viewers.  The Dutch viewers at Bellevue that were clearly better
were around $400 or 500, and even though I highly value my views & my
optics, I didn't make that investment.  But it is great that they are out
there, so people can see the possibilities.
_______________________________________
Peter Abrahams   telscope@xxxxxxxxxx
the history of the telescope, the microscope,
    and the prism binocular


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