Celestial Navigation: The Sea Astrolabe

The sea astrolabe was a brass tool constructed and used for the purpose of determining one’s latitude. Most commonly, it was used on long marine voyages that required knowledge of the ship’s exact whereabouts in order to continue in the correct direction. The astrolabe measures the altitude of the sun at noontime or the meridian altitude of a star that has a known declination (or altitude). It could withstand the boat’s rocking in rough seas and intense winds, which a previous model called, simply, “the astrolabe”, was not able to endure. The instrument was beneficial to marine exploration, although it did have some limitations; wind was still an issue and until later improvements were made, the alidade (see photo) was not long enough to provide a high angular accuracy.

 

The Sea Astrolabe (view 2)

The Alidade

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3 thoughts on “Celestial Navigation: The Sea Astrolabe

  1. I think it is interesting that to use the sea astrolabe, sailors needed to study the sky. Knowing which star is at a certain altitude or judging the Sun’s altitude at different latitude all relied on prior knowledge of astronomy. The sea astrolabe truly is a fascinating instrument to make use of this knowledge.
    Even though today’s navigation technology that may not rely astronomy, it is cool to see how humans used astronomy and for what purpose.

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  2. It is interesting to me that much of the exploration of our planet would not have been possible without astronomical knowledge. I have not thought much about the practical applications of astronomy in a historical context, but this is certainly one of them.

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  3. It is amazing to think how far humans have come in the realm of navigation since this time. This did the same type of thing (with less precision and detail) than our modern GPS but got people to their destination nonetheless.

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