When Was The 'Sextant' Invented?

In the year 1731, the Sextant was invented by John Hadley. Generally speaking, the sextant is used at sea to determine the distance of a ship from the Equator or in other words to calculate the ship's latitude.

Sextant was the instrument, whose invention paved the path for modern navigation to gain momentum with the help of the sun and the stars.

The instrument got its name from the fact that it is equippeded with an arc that is usually one-sixth of a circle or more precisely 60 degrees (a circle has 360 degrees in total). It measures the angle of the sun's or a star's height above the horizon. As this angle varies with distance from the Equator, it helps the navigator to provide him the accurate point of his position, or the latitude that he is on. The rest is accomplished by determining the time, the date and the longitude, which could easily be found by comparing the local time with the time at Greenwich.

Made in 1731 by John Hadley. A Sextant is a tool used to measure the angle between any two observable objects. The primary use of a Sextant is to measure the angle between a celestial object and the horizon, doing so gives us the latitude. Making this measurement is recognized as shooting an object or taking a sight. The Sextant can be used to measure the lunar distance and any other celestial object which would give us the Greenwich Time.  Isaac Newton invented the Octant which is related to the Sextant but never published it.

1731 by John Hadley.

1731

If Hadley and Godfrey both invented the octant (the predecessor to the sextant) in 1730, though Newton actually had it in 1699, though his publisher Halley, did not get it published until 1742. It is doubtful that the sextant was developed in under a year, because Caleb Smith,had created an octant in 1734.He called it an Astroscope or Sea-Quadrant.His used a fixed prism in addition to an index mirror to provide reflective elements. So, if the octant was still being developed upon, the sextant had to have come much later, sometime between 1767 and 1780,
'In 1767 the first edition of the Nautical Almanac, tabulated lunar distances, enabling navigators to find the current time from the angle between the sun and the moon. This angle is sometimes larger than 90°, and thus not possible to measure with an octant. For that reason, Admiral John Campbell, who conducted shipboard experiments with the lunar distance method, suggested a larger instrument and the sextant was developed'. (taken from wiki en.wikipedia.org Demise of the octant.)