Société des Lunetiers theodolite

The mid 19th century Société des Lunetiers simple theodolite
Figure 1: The mid 19th century Société des Lunetiers simple theodolite
I've obtained this theodolite on a trip to Egypt in 1994. The instrument is of French origin and was used for simple measurements, probably in construction works. As it lacks a vertical scale it might be better to call it a cercle d'alignement (alignment circle).1

The instrument was manufactured by the Société des Lunetiers in its manufacturing plant called La Compasserie.

The sexagesimal divided circle is read down to 1/30th of half a degree or 1 arc minute, similar to the K&E transit in my collection. The reticle has the same lay-out as the transit, but despite being older than it, the cross-hairs are etched rather than made of cobweb.

The telescope can be transited in one direction only by turning it with the objective downwards. The ocular side of the telescope is too long to be transited. The instrument has a scope mounted at a 90 degree angle with the telescope for setting out 90 degree angles in an easy but coarse way.

Thanks to a clamp and drive screw at the bottom of the primary axis the instrument can be used as a repetition theodolite, allowing to measure angles at a higher accuracy.

In overall design the instruments looks quite similar like the mid 19th century Egault level by Secrétan à Paris in my collection.

Notes

[1]: Géomusée: Le musée des géomètres-experts de la Région Rhône-Alpes en France.


If you have any questions and/or remarks please let me know.

The vial of the instrument
Figure 2: The vial of the instrument
 
The horizontal circle reading 331°53'
Figure 3: The horizontal circle reading 331°53'

The inverted view through the telescope revealing two stadia hairs on the etched reticle.
Figure 4: The inverted view through the telescope revealing two stadia hairs on the etched reticle.
 
A look through the perpendicular scope.
Figure 5: A look through the perpendicular scope.

Surveyor's crosses Geodetic Sextants Theodolites Total Stations Levels Standards Tools Firms
19th C. SDL 1919 K&E 1926 Zeiss RThII 1924 Zeiss Th1 1929 Wild T2 1937 Wild T3 (astronomic) 1939 Wild T3 (geodetic) 1943 CT&S Tavistock 1948 Wild T1 1952 Wild RDH 1956 Wild T0 1961 Wild T1A 1961 Wild MIL-ABLE T2 1962 Wild T2 1963 Wild RDS 1966 Kern DKM2 1969 Wild T2E 20th c. Askania Tu400 1990 Wild T2 mod