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Inventory no. 54253 - Epact entry

Epact number: 26741

Mariner's Astrolabe

Unsigned
Later 16th century; Spanish ?
Bronze; 184 mm in diameter

Main text

Like many surviving mariner's astrolabes, this example was brought up from the sea bed. The instrument was found during dredging work in 1903 at Vera Cruz harbour in the Gulf of Mexico. Only the cast bronze circle and suspension were recovered; the alidade is a modern replacement.

There is a scale for both altitude and zenith distance in the upper left quadrant. The only other marking on the instrument is an unidentified 'A' surmounted by a star at the base of the lower ballast section.




Source museum: Museum of the History of Science, Oxford
Museum number: Inventory no. 36,457



Detailed text

The instrument is of cast bronze with a shackle and suspension ring. There are three spokes and a lower ballast piece with a heart-shaped void. At the base of the ballast is an unidentified mark: an A surmounted by a star.

Around the circumference of the limb are engraved circles. There is a scale in the upper left quadrant, divided to 10, 5 and 1 and numbered 0 to 90 by 10 in both directions, for altitude and zenith distance. There is a '5' between each of the pairs of 10ยบ numbers.

The reverse is blank and the alidade and fixing pin are modern replacements.

The instrument was found during dredging work in 1903 at Vera Cruz harbour in the Gulf of Mexico. This location and the diameter of approximately 8 Spanish inches have suggested a Spanish origin.

The instrument was purchased from its finder Donald Courie by R. T. Gunther.

See A. Stimson, The Mariner's Astrolabe (Utrecht, 1988), p. 68.

Stephen Johnston

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