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Archives of an email list on the history of binoculars. - page 45 / 150

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--Visiting several stores retailing telescopes & binoculars:

Kokusai Kohki in Kyoto, whose owner, Barry Gooley, was kind enough to drive me to a 'Star Party' outside Kyoto.

In Tokyo, Mr. Tanabe provided me with maps to three telescope stores: 'Kyoei', 'Seihosha', and 'Takahashi Star Base Tokyo'.

The Takahashi store was the best, I knew I had arrived when I saw one of their 22 x 60 models on a tripod, displayed outside, on the sidewalk.

In the three stores, I inspected many binoculars, including:

Nikon has two new roof prism models, a 10 x 25, and an 8 x 20 that I liked very much except it was $500, $450 retail; with excellent images - a wide & flat field.  (Prices were of course in Yen.)

I compared them to the Kowa BD25-8, 8 x 25, 6.3 degree, $240. retail, which is very good but not at the level of the Nikons.

  I also used a Nikon 15 x 70, 4 degree field, with excellent images; I don't believe this model has been sold in the U.S.

It is better than the Nikon 18 x 70, 4 degree field, which is very good but has some distortion & edge problems; retail $1100.  (Compared to the Nikon 10 x 70 at $640., which is excellent but narrow field of view.)

  Fuji has released a new 16 x 70, shorter & smaller, but with inferior images compared to their old 16 x 70: low distortion, moderate field curvature, some odd effects of illumination at the edge of the field that I can't describe, reflections off surface of the eye lens were distracting, and uncomfortable eyecups.

--I gave a talk in Tokyo on the history of binocular telescopes from 1600, which had been translated into Japanese for a handout.  Nishioka & Tanabe were in attendance, as was Toshiya Kamakura.  I also met Takashi Nagajima, who is writing a series of articles on historic binoculars for the Japanese magazine 'Sky Traveler'; the most recent issue has the 81st article in the series.  Hopefull, one day we can translate these articles.

  Without the assistance of my Japanese hosts, I could never have seen & learned all that I experienced, and I am grateful for their efforts.  We are all aware of the achievements of Japanese optical engineers & manufacturers, but the background to this is almost totally unknown.  It will take a lot of work to publish the history of modern Japanese binocular production.     --Peter

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Binocular List #265: 21 August 2003

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Subject: Eastern European optics

From: "Forrest" <forrest@___crimoptical.com>

  I was involved in the design of a spotting scope about 10 years ago and when evaluating prototypes we were puzzled by its yellowish hue.  Almost like it had a slight yellow filter.  After much analysis of absorption of various wavelengths from the Schott glasses used we concluded that would not account for this aberration.  Finally using Zemax software we were able to show the effect is caused from sphero-chromatism in the exit pupil.  It was eliminated by redesign which was both validated on paper with the program as well as with the first prototypes.  This was a very unusual optical problem which our chief design engineer has not experienced in his 40 years of optical design.  I just thought your readers might consider this as possibly a similar problem with the Russian design mentioned on the binocular list #264.

Forrest Babcock

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