| Instrument | : | Theodolite type Th42 |
| Manufacturer | : | Carl Zeiss |
| Country of origin | : | West Germany |
| Manufacturing year | : | Second half 20th century |
I've obtained this theodolite in 2008. I swapped it with a former colleague for a Wild T2 that I had double and he used to work with. The instrument was manufactured by Carl Zeiss and was 'Made in West Germany'. The history of Carl Zeiss goes back to 1846 when Carl Zeiss opened his first workshop at Neugasse 7, Jena (in what would become known as East Germany after WWII). Before the end of WWII there were two workshops; one in Jena and one in Oberkochen (in what would become known as West Germany after WWII). This instrument came from the West Germany factory at Oberkochen and was made there somewhere between 1975 (date of patent of the instrument's base) and 1990 (reunification of Jena and Oberkochen factories after the fall of the Berlin wall in 1989).
The instrument was a third order instrument, meant for builders, simple stake-out work and lower order land surveying (see 'Einsatzgebiete' in fig. 13).
The Th42 shown here must have been an early one. As can be seen on the product flyer the instrument has two adapters on top of the instrument, to hold an Eldi distance meter. Both sides of the instrument on the flyer are equal in height in order to have the two adapters in the same horizontal plane. The instrument in my collection is unequal in height and lacks any remaining holes that would have held the adapters. Instead two aluminium brackets with the adapters have been fastened to it to make it compatible with the one on the flyer. The Eldi distance meter was made in three different versions; the Eldi 1 would measure up to 5000 metres, while the 2 would reach 3000 metres. The Eldi 3 had a 1500 metres range.[1]
Both the horizontal and vertical circles of the instrument are divided in gon (400 divisions in a full circle) and can be read down to 0.01gon (about 30 arc minutes) and estimated one further decimal. The instrument has a pendulum type compensator for the vertical scale.
The base of the instrument uses the same DIN 18719 stub and socket joint as the Askania Tu 400 in my collection (see fig. 4). The base itself consists of two parts, connected by a ball joint for quick and rough levelling. Only two levelling screws are available for the final levelling of the instrument.
In 1977 the instrument would have cost fl.7323.-[1]
I am looking for further information of this instrument:
[1]: Thanks to John Vossepoel for the pricing and the information on the Eldi distance meters and the accompanying brochures.