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Jovian Eclipse

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A Jovian eclipse occurs when one or more of the four moons of Jupiter passes behind the planet. In Cook's day measurements gained from observation of Jovian eclipses were used to calculate longitude.

Between 1610 and 1612, Galileo first observed the moons of Jupiter. On the basis of his obeervations he was able to create tables that accurately predicted the movement of these satelites. By the late seventeenth century, Giovanni Domenico Cassini, working at the Paris observatory, had used careful observations of Io, Jupiter's closest moon, to create a series of tables that could be used to determine longitude with a great degree of accuracy.

However, this method of determining longitude could not be used at sea because even in the calmest weather, the movements of a ship made it impossible to gain accurate readings of the position Io or the other three moons during the course of an eclipse.

Related Entries for Jovian Eclipse
Natural Phenomena: Io
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Prepared by: Paul Turnbull
Created: 5 May 2004

Published by South Seas, 1 February 2004
Comments, questions, corrections and additions: Paul.Turnbull@jcu.edu.au
Prepared by: Paul Turnbull
Updated: 28 June 2004
To cite this page use: http://nla.gov.au/nla.cs-ss-biogs-P000419

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