| record number: | 12 |
| instrument type: | precise level |
| manufacturer: | Carl Zeiss Jena |
| serial number: | 25470 |
| model: | Ni III |
| year of manufacture: | 1934 |
| instrument set up, special features: |
circular level
coincidence levelling toric level tilting screw with division, 100 units, turning the screw by one unit means changing the line of sight tilt for approx. 2,2'', the screw division unit represents a length constant of 1000 |
| Telescope | |
| diameter of objective: | 45 mm |
| magnification: | 36 x |
| type: | telescope with internal focusing |
| cross hairs/reticule: | crosshair of precision levellers - horizontal hair splits into a wedge, Reichenbach's distance meter, constant 100 |
| precision: | 0.5 mm/km |
The level was made in the mid-1940s. The coincidence levelling toric level enables the levelling of the line-of-sight axis. The level is rotatable (reversible) and is rotated together with the telescope. The tilting screw for the levelling of the level has a tilt micrometer. In a practical experiment, we found turning the micrometer by one unit means changing the tilt of the axis for 2.2''. This allows the instrument to measure distances quite precisely, the unit of the micrometer defining a constant of 1000.
To determine the fraction of the graduation unit on the staff, the instrument has a built-in micrometer with a plane parallel plate. This makes the instrument a precise level. The crosshairs have the shape that is typical of a precise level with a micrometer – the left side of the horizontal hair splits into a wedge. The precision of the instrument is 0.5 mm for 1 km double-run levelling.
The instrument was completely restored and partially lacquered in 2016 and is still fully functional.