1979 Observator Geodetic Sextant

The 1979 Observator Geodetic Sextant
Figure 1: The 1979 Observator Geodetic Sextant
I've obtained this geodetic sextant in 2000. An exceptional instrument as it has a centesimal scale (this means the scale is devided in the 400gon system, where 400gon equals a full circle, see figure 3). The drum micrometer is divided in centigrads (one hundreths of a gon) and can be estimated another decimal although that will be beyond the instrument's accuracy (see figure 5).

It also is exceptional in the fact that is has six legs to rest on, three of them on the telescope side. One of the legs is actually blocking a part of the view through the telescope (see figure 4). The other geodetic sextant by C. Plath in my collection has the legs mounted in a better way, so out of the telescope's path.

This type of sextant was first built in Sweden where it was used for geodetic network measurements on land along the coast. Later on it was also used by the KNMI (royal Dutch meteorological institute).

The handle has a threated hole, to make it possible to attached the instrument to a tripod or to attach a perpendicular handle. When using this perpendicular handle the instrument can't be laid down as usual on its back, so three additional legs are provided on the front to rest the instrument on.

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

 The rear of the instrument. The threated hole in the handle is clearly visible.
Figure 2: The rear of the instrument. The threated hole in the handle is clearly visible.
 
The drum micrometer reading 67.891gon.
Figure 3: The drum micrometer reading 67.891gon.

View from the front clearly showing one of the legs that stands in front of the telescope.
Figure 4: View from the front clearly showing one of the legs that stands in front of the telescope.
 
The manufacturer's name and logo (Observator).
Figure 5: The manufacturer's name and logo (Observator).

The instrument in its case.
Figure 6: The instrument in its case.
 
The calibration sheet dated June 22nd, 1979.
Figure 7: The calibration sheet dated June 22nd, 1979.

Surveyor's crosses Geodetic Sextants Theodolites Total Stations Levels Standards Tools Firms
1956 geodetic sextant 1979 geodetic sextant