Then the revised design of the roof prism makes the old, and probably fairly expensive steel castings dispendable. Now the tubes of the dialyt can be turned on a Lathe?
I think those thin wall steel castings must have had a fairly high fault rate in the production....they are extremely thin.
Michael Simonsen mikedenmark@___l.com
(I sent a copy of Michael's email to Hans Seeger. --Peter)
From: hans.t.seeger@___ne.de (Hans Seeger)
It is true that Dialytes were introduced in 1905, see my book on Feldstecher pages 108 - 109.
The remark on steel housings of late Pentaprism glasses refers to those with the "rounded shoulders", i. e. to models which have a one part prism housing like Abb. 115 and 116 in the book on Feldstecher and Abb. 67 (page 115) in my book on Military Binoculars. Earlier models of these had an aluminium body. I have a monocular of this shape with magnetic properties indicating a steel housing; I cannot tell if cast or steel sheet. The weight of this 12 x 26 (without serial number) is 240 g and would (to my feeling) not be much lighter with alu housing. The left hand glass in Abb. 67 has steel housings.
The explanation of some sort of layer on prisms caused by a volatile aluminium compound is very unlikely. Aluminium oxide is not volatile. Only in case of strong corrosion of aluminium this will be transformed into a white powder. Normally, a very thin and transparent aluminium oxide layer prevents oxidation of this metal. Therefore some manufacturers did not paint the interior of early binoculars in order to gain the impression of higher luminosity. --Hans
Subject: Recent imports
From: "Osborn Optical" <optical-repair@___t>
>> What is the story on the Kunming , etc copies of the East German copie/adaptations of the prewar Asembi? All these seem to be out of collimation, plus improper spacers, etc? Maybe Osborn will choose to shed some light on this topic. He was pushing those for a while.<<
Ah. So the new term for selling is "pushing". I suppose the term may be appropriate for optical addicts. At any rate, after about 200 units, it was noticed that the quality was indeed slipping. The last 50 or so, were definitely suffering from indifferent assembly. My last trip to the factory revealed that with the turning over of much of the factory from military control to privatization , the quality control was leaving as well. From our standpoint, they were not worth the work to continue importing. In my contact with other folks that are still handling them, they are having to put considerable work into them to be saleable.
>> Or the French modifications of the WW II Busch 10 x 80? He had some of those also.<<
I only had one French variation that I had taken in trade quite a while back (since sold), but, I may have another coming. They are fixed focus and have no filters. There is a desiccant cartridge inserted in the hole that the filter drive shafting used to occupy. The eyepiece lenses are the standard 10x80x45 degree lenses in a one piece, fixed focus cell. The objectives utilize a different cell as well with brass spacers and retainer rings. Some have the original prism housing, and others have been found with a different casting that incorporated an machined boss on the bottom that supports a synchro.
From "the top of the optical repair mountain" ;) , Earl
From: "William M. Beacom" <bbeacom@___.net>
The photocopied booklet I prepared has a page from the 1937 Geco Catalog#65 with 13 different models of RUKA binoculars in both regular and Leichtmetall. --Bill Beacom