a measuring instrument for measuring the angular distance between celestial objects; resembles an octant
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Sextant \Sex"tant\, n. [L. sextans, -antis, the sixth part of an as, fr. sextus sixth, sex six. See {Six}.] 1. (Math.) The sixth part of a circle.
2. An instrument for measuring angular distances between objects, -- used esp. at sea, for ascertaining the latitude and longitude. It is constructed on the same optical principle as Hadley's quadrant, but usually of metal, with a nicer graduation, telescopic sight, and its arc the sixth, and sometimes the third, part of a circle. See {Quadrant}.
3. (Astron.) The constellation Sextans.
{Box sextant}, a small sextant inclosed in a cylindrical case to make it more portable.
Neither did it record the systematic sextant readings necessary to determine one's position relative to the sun, Herbert said.
Aside from the mirrors and the other precision hardware, Hughes also supplied the telescope's fine-guidance sensors, which work like an ultra-precise sextant to allow the telescope to literally steer by the stars.