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The History Of The Sextant

Exciting news here at Chart Sales this week – we’re about to start selling sextants and clocks, as well as other marine navigation equipment… so if this is what you’ve been keen to invest in, you’re certainly in luck.

Sextants are navigation instruments that were used to measure angles, especially the altitudes of the stars and sun above the horizon, in order to help people find their positions on earth.

A marine sextant (as opposed to an air sextant) is made of a triangular frame with a curved scale at the bottom. The frame boasts an eyepiece and a piece of glass – or the horizon mirror – with one half clear and one half silver.

You hold the instrument so that you can see the horizon through the clear glass when you look through the eyepiece. There’s a movable arm with a second mirror on it that’s attached to the frame and which crosses the scale.

You can position the arm so that the image of the sun appears in the horizon mirror, so it looks like it’s touching the horizon. You then read the position of the arm in order to find out the altitude of the sun in degrees.

The name ‘sextant’ comes from the Latin sextus, meaning ‘one-sixth’, referring to the arc which spans 60 degrees.

The instruments were central to the success of navigation and sailing for many, many moons – and although celestial navigation has now been relegated to the history books, they’re still beautiful instruments to look at and collect. And there are still many out there who take real pride in being able to navigate their way using them.

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