R & A Rost Wien
theodolite R & A Rost Wien
record number: 16
instrument type: theodolite
manufacturer: R & A Rost Wien
serial number: 3620
weight: 6.12 kg
dimensions (l/w/h): 24/21/27 cm
year of manufacture: 1890
centering and leveling the instrument: plumb bob
two perpendicular toric levels on the alidade
vertical circle: vertical circle level, tilting screw
precise reversible level - levelling toric level

The theodolite was manufactured at the beginning of the 20th century and was used until the 1960s. The instrument is very complex, as can be seen from the number and types of toric levels: two alidade levels, a vertical circle level and a reversible levelling toric level. The closed protected horizontal circle has a base interval of 10'. A special feature is the diametrically positioned screw microscopes (German: Schraubenmikroskop) with associated micrometer screws, which allow the determination of fine readings with a resolution of 10''. This method of determining a fraction of the graduation unit of the division, which appeared in theodolites at the turn of the century, significantly increased the resolution of the instrument. In the vertical circle the vernier is read with a microscope and the resolution is six times lower.

The instrument was fully restored and partially lacquered in 2016. Two new diaphragms and one frame are added to illuminate the division of the circles, and the modular toric level is renovated.

Characteristics
horizontal circle vertical circle
diameter: protected, 14 cm unprotected, 10 cm
type of division: engraved division engraved division
limb implementation: silvered metal bracket silvered metal bracket
division: sexagesimal/sexadecimal sexagesimal/sexadecimal
unit: 10' 20'
Reading
number of reading points: 2 2
reading device: screw microscope vernier
number of units: 60 20
graduation unit: 10'' 1'
repetition: clamping and micrometer screw /
Telescope
diameter of objective: 30 mm
magnification: 17 x
type: Ramsden's retractable eyepiece
cross hairs/reticule: Reichenbach's crosshairs, constant 100