What's a sextant used for?

Sailors have always had to solve the problem of knowing where the position of the ship.

The first instrument able to answer this demand was the astrolabe, examples of which had already been found in the wreckage of a Greek vessel of the IV century BC. A development of this device was the sextant, an instrument that is used to calculate the position of a ship.

Who invented the sextant?

The nautical sextant considered one of the most important inventions of the Middle Ages was invented by John Bird at the request of John Campbell in 1757. This invention replaced the astrolabe, which was less accurate and had been of great importance for many exploration voyages and the developments in sailings as it had been the main instrument to measure latitude for many years.

How does a sextant work?

It's made up of a a circumference arch -a sixth of a circumference, from here its name-

provided with a small spyglass or telescope and two mirrors; one is permanently fixed and the other movable.

It's used in this way: you address the spyglass towards a previously chosen star, after you turn the instrument so that the star's image appears reflected on the movable mirror. Then you turn the instrument until the image of the reflected star appears on the horizon; you look how much the instrument has turned and so measure the height of the star.

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The following post is about A SEXTANT WITH HISTORY: a sextant that belonged to my grandfather.