Ertel & Sohn München
theodolite Ertel & Sohn München
record number: 11
instrument type: theodolite
manufacturer: Ertel & Sohn München
serial number: 32156
weight: 8.99 kg
dimensions (l/w/h): 37/28/41 cm
year of manufacture: 1900
centering and leveling the instrument: plumb bob
two perpendicular toric levels on the alidade
centrally set circular level
vertical circle level, tilting screw
precise reversible level on telescope
striding level adjustable to telescope supporting column

The tacheometer-theodolite is one of the most sophisticated theodolites of its time. It was made at the beginning of the 20th century. It stands out for its complexity and precision in measuring horizontal directions. Worthy of mention are the number and types of levels: a circular level, two horizontal circle (alidade) toric levels, a reversible levelling toric level, a striding level and a vertical circle level. The horizontal circle with a diameter of 18 cm and the reading of the division at two diametral points with a screw microscope (German: Schraubenmikroskop) with a micrometer screw provide an incredible resolution of mechanical determination of the reading, i.e., 1''.

The theodolite was still used in the 1960s for measurements in trigonometric nets of lower orders. In 2016, the instrument was completely restored and lacquered, and a new frame for the diaphragm and mirror for the striding level were made.

Characteristics
horizontal circle vertical circle
diameter: protected, closed, 18 cm protected, 15 cm
type of division: engraved division engraved division
limb implementation: silvered metal bracket silvered metal bracket
division: sexagesimal/sexadecimal sexagesimal/sexadecimal
unit: 10' 10'
Reading
number of reading points: 2 2
reading device: screw microscope vernier
number of units: division of the graduation unit into 5 parts, a fifth is 120 units 60
graduation unit: 1'' 10''
repetition: clamping and micrometer screw /
Telescope
diameter of objective: 30 mm
magnification: 17 x
type: telescope with internal focusing
cross hairs/reticule: Reichenbach's crosshairs, constant 100