Long german WW2 optic , what is it ?

[trader]

Hello All,

I have this long German WW2 optical device , about 2 meters long and have no idea what it was used for. All help greatly appreciated in identifing it.

Thanks in advance.

Trader ( charnuska@yahoo.com )

[zeissasembi]

Maybe an older version of what you find here
https://picasaweb.google.com/MapTack...07169904818626

[trader]

Thanks

Thanks a lot , sure appears to be exactly that. Appreciate it.

trader

[globbitz]

Hello trader,

Yes, definitely a Zeiss 2-metre Subtense Bar.

These were used in the 1950s through to 1970s (and beyond) for surveying for distance measurement by setting it up on a tripod at some distance from the observer, and using the optic within the Subtense bar (in your second picture) to ensure that the bar is exactly perpendicular to the observer (who would have a 1-second accuracy theodolite). In many respects the Subtense bar is a more-accurate version of a Bassislatte that would be used to calibrate a rangefinder, and I'm certain that's where the idea for the subtense bar originated.

Inside each half of the rod there is an invar metal rod and that will not expand in different temperatures (unlike other metals), so that the distance between the markings is exactly 2 metres. You'll need a Zeiss Tribrach with a 34mm hole in the top to be able to use the Subtense bar in order to be able to mount it on top of a Tripod.

Once setup, the observer will then measure the angle from his position to each end of the 2m markings on the Subtense bar, and do a bit of Pythagoras, and hey-presto you'll get the distance from Observer to the centre-point of the bar.

Ideally the Observer would move his Theodolite to two or more different positions in order to triangulate in order to get an average on the distance and avoid error - each time the Subtense bar would need to be re-oriented to face towards the observer. It was a time-consuming task, but the Subtense bar method was the most-accurate method of measuring distances before lasers came into general use in the 1970s. A Theodolite of 1-second angular accuracy was a minimum requirement, however.

There were at least four other methods of measuring distances in this period, using different specialised Theodolites in conjunction with Vertical or Horizontal measurement staves, plus Wild, Barr & Stoud, and Hilger & Watts also offered specialised 'Surveying Rangefinders' until approx the late 1960s.

I'm planning to launch a website concerning 'Rangefinding and Optical Distance Measurement' in Summer next year which will include the Subtense Bar along with all other Surveying methods of the Post-War period in addition to a sample of 'Man-Portable' Rangefinding devices from 19th Century to Cold-War period.

Best regards,
Paul

[Lorenz SZ-42]

Looks DDR

regards
Lorenz

[globbitz]

Hello Lorenz,

Yes indeed, Carl Zeiss Jena were in East Germany. The 1Q marking was a designation to indicate the finest quality on their export products.

The dark-green colour was typically applied to their initial Surveying products Post-War, such as the Theo 010 (1-second accuracy, typically used with the Bala 2m), the Theo 020, and Theo 030 Theodolites (I'm sure that there were other models too). The same green was also applied to their Levels and accessories until (I think, the 1960s). They then applied a light-grey on their products until sometime in the 1970s when they elected to change to a yellow/orange thus making the products highly visible within the building site environment.

The 2m Bala in my collection is grey for example, so the green model in the photos would indicate that it's an earlier model more-likely used with a Theo 010 dating back to the early 1950s through to the 1960s.

Best regards,
Paul