Binocular eyepiece adapters for telescopes.   By Peter Abrahams

Binocular attachments for microscopes have been made since the early 1800s.  
The idea of attaching one to a telescope probably occurred soon after, but the 
earliest known documentation of this is from 1865.

1865.   Tolles, Robert B.  Method of applying the binocular principle to the 
eye-piece of a Microscope or Telescope.  American Journal of Science (2nd. 
series) 39 (1865) 212-215.  pp215, "Applied to the telescope, the binocular 
eye-piece...Its utility, as thus applied to those telescopes...is too obvious 
and striking to need remark.  The view thus obtained is truly stereoscopic."  
Patent 56,125;  03 July, 1866.

1866.  Mr. Troward of Doncaster "has used the microscope as a binocular eye 
piece to a (reflecting) telescope for three years"  Astronomical Register #42 
(June 1866) p152.

1876.  "Mr. Thornthwaite was called upon to describe a binocular eyepiece, 
which he exhibited to the meeting.  The eyes, he said, were greatly relieved by 
making use fo such an eye piece, and the appearance of rotundity which 
telescopic objects assumed was very pleasing; the effect must be seen to be 
appreciated.  Astronomical Register 14 (Nov. 10, 1876) 291.

Zeiss:
-1920,  Catalog Astro 30, p66, Binocular eyepiece (two cylindrical housings for 
Porro prisms, provides erect image).  Model codeword (for ordering by 
telegraph): 'Ascetaria'.  For eyepieces 25mm to 5mm focus; used with or without 
diagonal prism.   1920, Astro 33, Astronomical Accessories, p20.
-1921, Astro 28, p16, adds note, 'Tube reduction 110mm'.
-1922, Astro 61e, & 1923, Astro 62: notes catalog 'Astro 48, Binocular Eyepiece 
for terrestrial and astronomical Telescopes'.
-1928, Astro 80, p39.  Adds model 'Asgol', 'Binocular eyepiece for astronomical 
  observations, available for use with eyepieces from 50 - 5 mm focus.  Non 
  erecting prisms'.  Two prism housings, first attached to diagonal is about 3cm 
  x 3cm x 7cm; second swivels atop the first & holds the right eyepiece; left 
  eyepiece in a lengthened tube directly attaches to first housing.
  Prices: Ascetaria $113; Asgol $137.
    "Binocular eyepieces: Many telescope users are unaccustomed to observe 
  with one eye, and their eyes may become fatigued through muscular strain.  It 
  is also generally admitted that in consequence of the habitual use of both 
  eyes, details in the telescopic image are less perfectly perceived by monocular 
  vision than is the case when both eyes participate.  A single tube telescope 
  may be given the advantage of the double telescope by equipping it with a 
  binocular eyepiece.  There is a terrestrial and an astronomical binocular 
  eyepiece.  Both double the image for observation with two eyes.  Besides this, 
  the terrestrial binocular eyepiece also erects the image into the natural 
  position.  For any desired magnification, two astronomical eyepieces of like 
  focal length should be specified in the order."
-1935, Astro 94e, p39.   1936, Astro 94, p39.   Same as 1928.    
-1937, Astro 527I, p11. One model only, 'Binokulares Okular Nr. 124', 
appearance of Ascetaria.

1927.  George E. Hale.  Spectrohelioscope, binocular eyepiece.  Scientific 
American 136 (March 1927) 186.

1950s.  Gerard Kuiper.  "During the 1950's...Gerard Kuiper observed the Moon 
and planets with this binocular eyepiece he made for the 40 inch Yerkes 
refractor and 82 inch reflector at McDonald Observatory".  Sky & Telescope, 
June 1985, p572.

1957.  Brayton Optical Exchange, Monterey, Calif.  Binocular eyepiece holder, 
1.25", $195.  Sky & Telescope, October 1957.

1974.  Ralph Dakin.  Maksutov Club Circular #178.

1975-6.  Tuthill.

1981.  Oscar Knab.    Telescope Making #11 (1981) 26. 

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May 2003
home page:    http://home.europa.com/~telscope/binotele.htm