Who invented the sextant?

John Bird invented the sextant in 1759. His work was based on prior work by John Hadley and Thomas Godfrey, who separately invented the octant. He also relied on the work of Sir Isaac Newton regarding the principles of a doubly reflecting navigation instrument.

Sextants are used to measure the angle between any two objects. They are typically used in celestial navigation to determine an object's altitude or the angle between a celestial object and the horizon. Taking these measurements allows the user to chart a position on a nautical chart. A sextant can be used to determine latitude when a sighting is taken of the sun at noon or of the North Star at night.