The word sextant comes from the Latin word “sextus” which means one-sixth. The sextant is an instrument used for measuring angles, primarily altitudes of celestial bodies like the sun or a star. It is also used in navigating ships and planes to determine the latitude. The height of the tall buildings and pillars can also be measured with the help of a sextant.
Sextant was invented by an Englishman, John Hadley in 1731. The device consists of an arc of a circle, which is usually one-sixth of a circle or 60 degrees, and a movable radial arm pivoted at the centre. A movable mirror is fixed at the end of the arm. The other end extends to the scale. A telescope is mounted on the sextant, and a glass mirror is mounted in front of the telescope.
To operate the sextant, the operator looks through the telescope straight at the horizon. Moving the mirror, the sun or any particular star is made to appear exactly on the horizon. The arm which moves the mirrors gives the required measurement of the angle. From this angle and the exact time of the day, the latitude is determined by means of published tables.
The invention of sextant has laid the foundation of modern navigation.