- an astronomical instrument used to determine latitude and longitude at sea by measuring angular distances, especially the altitudes of sun, moon, and stars.
- the constellation Sextans.
- an optical instrument used in navigation and consisting of a telescope through which a sighting of a heavenly body is taken, with protractors for determining its angular distance above the horizon or from another heavenly body
- a sixth part of a circle having an arc which subtends an angle of 60°
