Presentation Session Grand Big Binoculars World The history of Nippon Kogaku began with binoculars. In Nikon Kenkyukai Tokyo, many binoculars have been taken up to the theme of research. The Nikon Kenkyukai reported research on big old binoculars two years ago, in October 2010. Historical / Optical Study of Big Binocular Telescope in the Showa Era Many Nippon Kogaku enthusiasts said that this report was very interesting. The Nikon Kenkyukai Tokyo Meeting in June 2012 was held in Harumi near Tokyo Bay and we researched the historical old vintage NIKKO big binoculars again.
The Program of a Study Meeting Presentation Session Shigeki Terada, an engineering specialist of the Dodaira astronomical observatory, a member of the Nikon Kenkyukai Tokyo, a director of the telescope division talked about his great work. Let's enjoy a presentation program in Tokyo Meeting together.
Shigeki Terada's Excellent Presentation You can download his pdf document. Please understand his lecture, looking at this pdf document. Now, please start Terada-san lecture. Special Download
A Historical and Optical Study of Big Binocular Telescope in the Showa Era - Part 2 -
- Part 2 - In the last paper, I reported about pre-WWII High view angle binocular telescope and Showa 30' era (around 1955) binocular telescope. Recently, I have got some new samples and then had chances to restore and investigate those samples. I would like to describe some topics that I found out during those restorations.
Sample No. 1 : This is owned by Choukou soy sauce and soy paste manufacturing association, Ohmura-cho, Nagasaki Prefecture. I got a chance to restore it from February 2010. Specified Model of Nikko local code is "JOG high view angle binoculars" and IJA code is "model 89 10 cm Anti-aircraft binoculars". Serial No. is 2011, And there are some engravings on the body. Assumed manufactured period is Showa-17 (1942), made at their Ohmiya plant, Saitama prefecture. Because Enomoto was absorbed by Fuji photographic film in 1943, using glasses are assumed made by Fuji optical glass. But glass n-Abbe number measurement of rhomboid prism by spectrometer is indicated BK7, and glass maker seems to Nikko glass according to REPORTS OF THE U. S. NAVAL TECHNICAL MISSION TO JAPAN (Ref.: USNTMJ Report X-05). Optically, this is very similar to Nikko's same model that last time mentioned, but rhomboid prism is not silvered. Objective and eyepiece design are also very similar to Nikko's, but curvature is slightly different. This difference is indicated curvature standard is not Nikko's but Enomoto's. Hence, this optics is made by Enomoto's optical works. Viewing Impression is very good, and any differences from Nikko's same model are not found. This result shows Enomoto's high engineering level. Enomoto is former Fujinon! Also mechanically, compatibility with Nikko's is almost perfect. Original painting color is hidden inside of the lens shade of objective. It is IJA's yellowish gray. But repainted to IJA's dark green. Fork mount is made by Nikko. Serial No. is 3925. Fork is made with aluminum alloy except bronze screw, and horizontal indicator is made with bronze.
Sample No. 2 : This is the one reported last time. Model is same as sample No. 1. Serial No. 274. The year of manufacture is Showa-12 (1937). Another same model which a guest showed us on the day is serial No. 4069. It seems that the year of manufacture is Showa-14 (1939).
Sample No. 3 : Serial No. 8015. Because trademark is pointed out it is made after WWII. It seems that the year of manufacture is Showa-33 (1958). Specified model is "JF high view angle binoculars II" (standardized model). All transparent surfaces of optics are mono layer coated. Desiccation control is done by silica gel and moisture indicator (CoCl2 paper). Mechanically, the mating part to mounting is completely the same as the 12 cm 20x binocular telescope reported last time.
Sample No. 4 : Serial No. 504, it was manufactured in February Showa-20 (1945). It was six months before the deadly air raid on 7th August 1945. The specific model is "JF high view angle binoculars IV". This is not "Standardized model". One optical feature is its gigantic modified porro II prism. This optics consisted by porro II prism and rhomboid prism, so that optical pass became very long. It let upper prism of porro II be so big. And to make 20 deg. inclination, opposite side upper prism has unusual shape. Those glasses are very similar to Fuji's BK7. All optics is not coated. The viewing impression is very good, and similar to other 12 cm models. 20 deg. depression position is prominently comfortable. One mechanical feature is its much evidence of material shortage occurred in the last period of WWII. But it is not a "standardized model". Weight is 23 kg. Main body is made with poor quality aluminum alloy and machined roughly. To make it airtight, many mating parts are covered with waterproof clay and rubber seal. Bronze parts are found only around moving parts and screws facing outside. Furthermore, some inside parts are made with iron! The eye distance adjusting mechanism has the traces of the original "8" shaped steel belt around between 2 prism barrels, but there is no belt, and its right side (has a reticle) prism barrel is fixed, only left side can be moved. This sample has a rare wood container, and it contains bulbs for lighting its reticle. This bulb is made by Fuji electric, spec. is 20V2W-1cp (candlepower). Attached fork mounting and tripod are made by Nikko, serial No. 169, manufactured period is Showa-14 (1939). It is very heavy (34 kg), and all parts are made with bronze or brass, because anti-corrosion by seawater and before spread of using stainless steel. The opening distance of fork is 300 mm, it is for pre "standardized model" and cannot mount "standardized model". Desiccation control is done by same method as sample No. 3. However, cap is round screw cap.
12cm 20deg. 20x, Made by Toyokawa Naval Works
Sample No. 5 : This sample came from Sasebo, Nagasaki prefecture. There are no inscriptions. By distinctive shape of eye distance adjustment belt cover, this model specified to Model 65 type 12cm binoculars of Japan Maritime Self-Defense Force (Post WWII model of "JF binoculars type I"). Still now Kowa is using "8" shape steel belt to adjust eye distance and the cover of this belt dividable to 2 parts. This is not a "Standardized Model". All transparent parts of optics are applied mono layer anti-reflection coating. Hence, this is a post-WWII product. May be 1960's. Desiccation control is done by same manner as sample No. 3. Desiccant cap has a round shape but secured by 6 screws.
Sample No. 6 : This is the one reported last time. It has many characters of a "Standardized Model". Assumed manufacture period is 1957 because of serial No.7230. The specified model is the post-WWII model of "JF Binoculars Type I". There is a name plate "12cm binocular telescope type I" and triangular Nippon Kogaku Tokyo mark. This is the commercial model for the fishing industry etc. Desiccation control is done by same method as sample No.3.
Sample No. 7 :
This sample is owned by a member of Nikon Kenkyukai.
Serial No.114.
There is a inscription of Japanese letter "Mizu" (water) on the left prism case.
Then this is for a torpedo attack. Specified model is "JF Binoculars type III".
There is a sign "7. 12. 17"on the porro II prism by pencil,
this means the date 17th December Showa-7 (1932).
Probably, it should be manufactured in 1933. One optical feature is its 15x low magnification. By means of the 8 mm exit pupil diameter, Observer can avoid the misalignment of his eye pupil and exit pupil of eyepieces caused by the ship rolls and pitches. To achieve this magnification, its porro II prism becomes to extra big size. The glass index is very similar to Nikko's BK7. All optics is not coated. Viewing impression is excellent, because this low mag. helps to decrease relative chromatic aberration. Furthermore, flatness and distortion of the field of view is also very good. Mechanical features are its very heavy weight and gorgeous usage of every material. Lens shade and outer cell of objectives, big prism cases, every moving part is made of bronze. The body tube is made of very thick aluminum alloy. Weight is 23.5 kg. Eye distance adjusting mechanism is original "8" shaped steel belt around between 2 prism barrels and the adjusting screw scale. There is no desiccation control done by silica gel and moisture indicator (CoCl2 paper) except inner air exchanging holes. Desiccation control mechanism by silica gel and moisture indicator assumes to be applied from middle of 1930's. The design of mating part to mounting is differ from the high view angle binocular telescope. There is no elevation angle gauge and its indicator. Usually, high angle bino cannot balance to turn its objective horizontally, but this model balances to turn horizontally. Impression and Fact In addition, I would like to say my impression and fact through the research. 1. Nikko local codes There are some occasions that different Nikko local codes applied to one optical design. Those are assumed as one is for "Pre-Standardized model", another is for "Standardized model". 2. Compare with new Nikon Thanks to that day's guests, there is an opportunity to compare these old models with the brand-new Nikon 20x12cm binocular telescope type III (multi-coated). It is a matter of course Type III's extra high contrast obtained by its clean, multi-coated optics, but flatness and distortion of field of view have no difference. Because "Type III" is also "Usual" achromatic, the chromatic aberration is also similar to the old models. And type III's fork mount is completely compatible to "Standardized model"' such sample No. 3 and No. 6! This fact is very valuable. We can use the brand-new mounting for our old collections!! 3. Great German and Japanese old binoculars Also, the guest brought "eug" (The Optical Precision Works in Warsaw) 10x80 antiaircraft binoculars (with mono-layer antireflection coating). By comparison, viewing impression of eug is little better or similar to those Japanese models. It means optical part engineering level of the binoculars at that period in Japan is nearly attained to the world level. But machining engineering level seems obviously inferior to Zeiss. 4. Change of design And another guest brought "Pre-standardized model" 12cm 45deg. declination 20x High view angle binocular telescope. By comparison with the above No. 3 (Standardized model) , many KAIZEN of productivity points are found especially around prism cases. 5. Delay of radar development However, this outstanding significance of the binoculars technology development might mean the clear evidence of prevention of the radar technology progress in Japan. This time, fortunately, some precious samples from 1933 pre-WWII to 1945 final period of WWII, furthermore, post-WWII era could be investigated and compared. In this comparison, some technical transitions mentioned in literature were observed in the original. And some new findings are acquired. Especially, those samples showed the attitude to keep the primary objective - Optical Spec. - not only with gorgeous usage of materials and skills before WWII but also with the destitution of them in final era of WWII. During these restorations, I found some signs or imprints written by factory workers or soldiers of those days. They were alive in those days, and they really made, used and repaired these binoculars. This report should be a letter of thanks for their hardships and spirits.
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