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Subject: Binocular Repairman Recommendation

From: Leong J Tsang <l_tsang@___om>

  I have a CZJ 10 X 50 Jenoptiks that I bought for a friend for stargazing.

  In daylight conditions, the binocular appears to be razor sharp and steady.  However, when he uses it at nighttime for stargazing, he discovered that he is getting split images of the stars and anything that he views through it.

  Can you give me a list of good repairman who can tell me exactly what is wrong this binocular and what the cost will be to repair it.

  I am also looking for rear eyecups to use on the rear of the eyepiece of the binocular. Can you point me in the right direction as to whom is selling these.

Thanks in advance,

Evan Dong


We have several good repairmen & restorers on this list.  We haven't heard from them in a long time, and I don't know if they're accepting new work, or if they accept all sorts of binoculars for repair.  It would be helpful if they would address the list with a short paragraph about their services, location, and estimated waiting period for new jobs.

Thanks,     Peter


Subject: Prism binocular by Ahrens

From: Peter Abrahams

  A very unusual binocular, possibly from the 1880s, is shown in photographs on the web site.  Any further information on this subject is needed.

  Carston Diederich Ahrens was an important figure in late 19th century instrumentation who is quite overlooked today.  He does not appear in the Dictionary of Scientific Biography, nor in the British Dictionary of National Biography.  There are no entries in the Astrophysics Data System.  His major contributions were in microscopy, but he also designed & produced a hand held binocular telescope.  City directories cited by Turner (references below) include 1873, including: Ahrens, prism worker, 5 Baker Street, Lloyd Square, London; and 1874-1880, 373 Liverpool Road, London.  Ahrens noted that he made many hundreds of prisms for Wenham binocular microscopes, and also experimental prisms.

  Ahrens was granted English patent 1710284, 31 December 1884, for 'Improvements in the construction of erecting binocular prisms'.  This was similar to the earlier A.A. Boulanger design, using Porro I prisms, and without inspecting the patent, it is unclear what his improvement entailed (although von Rohr states that he did not complete the patent.)

  The Royal Microscopical Society collection includes a binocular eyepiece 295mm in length, with two eyepieces, by Ahrens, inscribed on the box:  "BINOCULAR EYEPIECE FOR HIGH POWERS. BY C.D. AHRENS, LONDON".  This was presented to the RMS by Ahrens, 31 October 1877.

A calcite prism in the lower tube causes a doubling of the image.  A 'double prism' of flint glass achromatizes the beam.  Interocular distance is adjutable by a rack & pinion.  

(RMS Accession no.: 1970-101/part, also marked RMS no. 54, Turner catalogue 416, Inventory no. 91539)

Museum History Science Oxford       http://www.mhs.ox.ac.uk/database/further.htm?Invno=91539

  Zeiss in Jena had an Ahrens binocular for inspection, cited by von Rohr.

  Another Ahrens binocular telescope, from the Louwman Collection of Historic Telescopes, can be seen in three small images:

     http://home.europa.com/~telscope/Ahrens-binocular1.jpg      28kb

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