Mariner’s Astrolabe

by Chris Carosa

The Age of Exploration might not have happened if…

The Story of the Barbary Corsairs by Stanley Lane-Poole and Lieut. J. D. Jerrold Kelley, G. P. PUTNAM’S SONS, 1890; Illustration Source: (Public Domain)

…sailors did not look to the heavens for guidance. And we don’t mean spiritual guidance, we mean real navigational guidance. The Mariner’s Astrolabe, the smaller and relatively more modern brother of those large, unwieldy ancient astronomical calculators known as planispheric astrolabes, allowed sea-going vessels to stay the course once they lost sight of land. Using a recognizable star, usually Polaris (the North Star) at night and the Sun during the day, the navigator would point the Astrolabe’s arm (the “Alidade”) at the star to determine the ship’s position (well, at least its latitude). Needless to say, without a mariner’s astrolabe (and not too many rainy days), east-west travel might have proved more dangerous (and less popular among a certain set of Pilgrims) during the Age of Exploration. Who knows where the world would be today without this small, but ingeniously practical, tool!

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