[photo-3d] ID an unusual old viewer

[Peter Abrahams <telscope@xxxxxxxxxx>]

Re: the pseudoscope shown at
http://home.europa.com/~telscope/viewer.jpg

>The other day, in a terminology discussion

I'm surprised I missed a discussion on history, even if it was cloaked in a
hypnotic sermon on teminology -- however, all I find in my files is this
(and surely when you say 'the other day' you couldn't mean 2 years?):
05 Jun 1999    From: abram klooswyk:  Charles Wheatstone... in 1852...
demonstrating an instrument ....called it the Pseudoscope..... prisms
mounted with the largest surfaces towards each other. 
----
>sure it is late 19th century and not early 20th? 

Without a maker's name, the dealer took an educated guess, but I think it
looks pre-20C -- the elaborate curved bevels on the brass and the style of
case look early.

>For pseudoscopes have been produced to view stereo x-rays, any size

The question would be, what other uses they had.  Using photographic
processes, a stereo pair could be produced that would view correctly with
this viewer.  Why would this system have been used?  Perhaps just the fact
that Wheatstone developed it is enough. (Drouin credits it to Dubosq.)  Or
perhaps it was used as a viewer that gave pseudo images, though I can't
imagine why except as an optical demonstration.
I can think of only one advantage this system would have, over a viewer
that is used on 'correctly' mounted images -- the prisms used in a pseudo
viewer could be much smaller than the rhomboid prisms used in a normal
viewer.  This could have been a significant factor in the late 1800s, when
the lack of suitable glass for prisms caused the Porro prism binocular to
remain unused from its invention in the 1850s until the development of
Schott glass for Zeiss binoculars in the 1890s.
Various configurations of mirrors were used in viewers, but at this date
the metal coatings did not endure.
I solicit any other clues on pseudoscopic viewers of the past.
--Peter

_______________________________________
Peter Abrahams   telscope@xxxxxxxxxx   The history of the telescope & 
   the binocular:   http://www.europa.com/~telscope/binotele.htm

 

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