This sextant, as are all (my) 400 gon sextants was specifically developed for use in surveying. Essentially the 400g or 400 gon is a method of dividing the circle in 400 units rather than the, in navigation, more usual 360 degrees. As a result this instrument, although indicating up to 140 gon is actually only around 125 degrees. This one still has the additional vertical handle for measuring horizontal rather than vertical angles. It is a drum sextant without a drum vernier allowing the angles to be read to 1 centigon. This one somehow ended up at a local yachting ship yard from where I got it. The leather on the telescope is still missing (loose) in the pictures shown but has been carefully glued back in place. The box has a slot for a prism, but as the sextant does not have the prism arm it is not probable that it was originally supplied with this sextant.

This instrument used to belong to Rijkswaterstaat and shows the label of the government survey vessel 'Capella' and the inventory number '103'. The Capella was a vessel of the Rijkswaterstaat department of the 'Northern Netherlands' whose area was the relatively shallow Waddenzee and Eems-Dollard estuary. The vessel was commisioned in 1972 (my year of birth) and it seems likely that the sextant was used before that in land surveying as I have another Plath geodetic sextant from those days from the central geodetic service of Rijkswaterstaat. However they probably never found much use in landsurveying and ended up on survey vessels such as the Capella. If it had been bought specifically for a survey vessel it would have been more logical to have a 360 degree version as this is more customary for hydrographic surveyors whereas the 400 gon is more custromary to land surveyors and geodesists.

More information / other collections:

de Hilster

MS Capella

De binnenvaart