generally assembled a rangefinder instrument.
(Here follows a detailed description on how to adjust and assemble a rangefinder.)
Finally I wanted to see a disassembled Inverttelemeter, 1.25 and 3 meters models. Unfortunately the german navy only uses stereotelemeters, and all inverttelemeters at the factory had been destroyed.
I did get to see the following instruments:
Stereotelemeters for the navy, 3 meter and 1.5 meter basis.
Stereotelemeters for the army 2 and 4 meter basis.
These instruments were assembled, but I saw drawings of a 1.5 stereotelemeter.
1.5 meter measures distances 1000-25000 meters
3 meter rangefinder measures 1500-30000 meters
Stereotelemeters has lamps for night uses, a sighting telescope and crude sights inlaid with "radiometal" which made them glowing in the dark.
1.5 meter has a height angle measurement, submerged in oil, for damping purpose.
The army 4 meter stereotelemeter has folding arms, one above, the other below the central part of the instrument. After unfolding the stereotelemeter must, of course, be adjusted.
Transport safety is the same for inverttelemeters and stereotelemeters.
The 4 meter must endure ½ an hour on a vibration table, which we saw in operation.
It seems to be a rather hard test.
( My comment: I have used similar equipment, it can destroy just about anything.)
( excluded here: More technical details on stereotelemeters.)
The principle of stereotelemeters was known before the war (WWI), but on demand from the german navy, it was kept a secret. Even the german army did only know little about this. The army did accept stereotelemeters during the war for anti aircraft targeting.
The Chief of that department told us, that he did measurement work for almost three weeks, before he suddenly acquired "stereotelescopic view" Since then, he has held the stereotelemeter to be better than inverttelemeters.
Another example is, that the chief of the construction office had problems with this. He finally went to an eye doctor, and it was found that one of his eyes had a 14 degree divergens.
This is also the maximum acceptable deviation for stereoscopic viewing, that the company had calculated theoretically.
We both had opportunity to try the stereoscopic rangefinding, and although we, the first day, was somewhat unsure of the concept, we did well on the second day and measured on distances of about 2000 meters. On larger distances our problems persisted.
(my comment: They most likely never really saw "stereoscopic" pride, nothing but pride)
In Germany there are special schools for rangefinders, and presently, there is a german navy officer at the factory, who is a teacher of a rangefinding school in Kiel ( Marinestation der Ostsee, or Baltic Naval Station ), and who himself is under education in stereometer range findings.
During the war, the german army had a rangefinder school in La Fere, Gent, with about 2000 pupils.
Finally, I can say that naval rangefinders 1.5 and 3 meters exists with periscopic oculars.
Production of graticules.
The factory believes the production of graticules to be very difficult and was reluctant to supply information.
They use 3 different methods:
1 Etching with acid.