Telescope Reviews: Do these Vintage Fujinos 150mm worth?

I have worked in and out of the illustrated 25 x 150 model since a few months after they were introduced , in 1973, and have used them for astronomy since that time. They were designed in the early 1970's, after a request by Ben Ichiyasu (RIP), whom I met about 1973 or 1974, for something bigger than the by then well-worn WW II Japanese military 20 x 120 , 15 x 120 ( highly prized, huge eyepieces and prisms), and others, including the postwar Nikon 20 x 120, essentially the same as a WW II Nikko 20 x 120, but with MgF2 coatings, in the tuna industry. Mr. Ichiyasu learned Japanese in the US Army during WW II, according to a long-ago conversation with his son.

The precursor of Fuji Photo Optical was Enomoto Kogaku, whose wartime mark is the same as the Star of David, with E.K. inside it. There may have been a 25 x 150 from them during the war. I have never seen one, though I have seen Nikko 25 x 150, of a different design. The illustrated model may have been a rebirth, rather than a completely new design. But the preceding speculation about the 1950's is not true, to the best of my knowledge .

There were EBC multicoatings on all air-glass surfaces in the 25 x 150 , since the 1973 or 1972 start, from my observation , and from the published specifications and promotional literature of that time. I am quite familiar with the internal surfaces of early specimens. The contrary speculation is erroneous. Cleaning multilayers requires more techniques and effort than single layer MgF2. The 15 x 80 has had single layer coatings in all postwar examples I have seen . I have several Fuji Meibo 25 x 150 I, and at least three of the Fuji Meibo 15 x 80. The 15 x 80 is used by the Coast Guard. I do not know if the current production of those is multilayer coated on all surfaces, or not. They have very good images across the field, and lots of eye relief, more than the 25 x 150 eye relief. The optics of the current Fuji 25 x 150 MT-SX, are the same as the optics of the trunnion version, I was told by the company at the time the current version was introduced, in the late 1980's or about 1990, as I recall. The trunnionless current version ones I have worked upon may have had slightly different coatings than the trunnion model, as there seemed to be a slight difference in the color of the residual reflections. I wonder what changes may have been required by the silly "no lead(Pb) in glass" regulations. A Japanese designer told me that there "are problems" several years ago at the Shot Show.

The early 25 x 150 trunnion model had brass focusing rings facing aluminum male multiple threads and near to aluminum pushrings, and several other brass-to aluminum interfaces, in the IPD bearings, and at the body-trunnion junctions. The resulting galvanic corrosion with the saltwater spray electrolyte lead to lots of profitable repair work for me . I machined Delrin and Celcon isolation rings and IPD link parts at an early stage. I showed the corrosion to an Ichiyasu around 1974 or 1975, and soon thereafter some brass was replaced by aluminum ,and the IPD link pivots became stainless steel. The brass trunnions were replaced by an aluminum- SS mixed assembly, perhaps a few years later. A few pounds were eliminated by these changes. I have a box of corroded pushrings and brass trunnions ( most shipboard mounts do not use the trunnions. The binoculars rest on thick elastic cords). The Inca doorway trapezoid shaped nameplate, SS, covers an aluminum coverplate for the dessicant bag housing. The early converplate screws were brass. Galvanic corrosion between dissimilar metals in the presence of seawater spray resulted in heavy pitting of the coverplastes. The brass screws became cemented in place by the corrosion product of the aluminum, in spite of the anodization of the aluminum. I have a collection of the trapezoidal stainless steel nameplates.

Speaking of anodization, those binoculars are an example of the superiority of the chromic acid process to the sulfuric acid process, in a marine environment, as was stated in the Fuji Meibo advertising. The Japanese production engineers got that part of the marine corrosion problem right. But I am glad that they used those brass-aluminum interfaces, particularly in the bearings, as that has caused much business for me. The early brass focus mechanism-aluminum prism housing coverplate corrosion was a big hassle. I lapped two in with Clover( automotive valve) lapping compound, in Latin America, about two years ago. I had filled the gaps and holes with metal-filled epoxy resin

Others attempted to permanently seal the rings and spacers around the objective barrel, using RTV silicone rubber, in close proximity to , or possibly even simultaneously applied, grease. That attempt only resulted in lots of unneccesary trouble in cleanup before eventually inevitable re-collimation after rough handling. There are inevitable clearances in lens assemblies of reasonable cost, for thermal reasons . There is considerably inertia in those large objective lens elements, and they move, if only slightly. during bumps, after time and thermal cycling. The resulting non-parallelism of the two optical axes can be easily seen with a handheld comparator. The current 25 x 150 version has a different system, prism sliding. The problem there is obtaining sufficiently fine motion. There is a lower limit to the pitch of available small screws for a compact mechanism. Eccentric rings and barrels , though more complicated to produce and to interface to each other precisely, allow finer adjustment by the technician. The WW II Nikko 18.8 x 150 ( I have one, used by David Rotbart to co-discover a comet ( with Ludmila Pajdusakova (later Mrkosova), of Skalnate Pleso Observatory in Slovakia. She used a WW II Zeiss 25 x 100, 60 deg. inclined view), and the Nikko 22.5& 30 x 180mm. used prism plate tilting.