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|Search result for definition: astrolabe|
|Astrolabe: A navigational instrument. It consisted of a dial, showing degrees, with an arm (alidade) pivoting through the centre. This arm, had a projection with a small hole on each end, you would line these up so a celestial body would be visible through both and the astrolabe's degree markings would indicate the celestial object's angle in the sky.|
It was used to determine a ships position by finding and predicting the position of the stars and the sun through triangulation. With the mariners astrolabe, latitude could be determined using the Pole Star or the Sun. It was the main navigational instrument until the invention of the sextant in the 16th century.