Sextants use a similar premise to astrolabes ... but this was very difficult to use on the deck of a moving ship.

We’ve also seen the future queen using a sextant — an astronomical instrument shaped like a 60-degree arc, used to measure ...

The approximate location of Endurance was logged by the ship’s captain, Frank Worsley, using a sextant and a theodolite at the spot where she eventually sank in 1915, after becoming trapped and ...