"Projects, curios and musings from the trailing edge" - a blog to complement the RetroMat website


Friday, May 29, 2026

Finding longitude before the invention of the marine chronometer

In recent posts about estimating the size of Astronomical Unit, I've stated that this couldn't have been done accurately before the advent of the marine chronometer to establish longitude.

Not so - it was the problem of the accurate measurement of longitude at sea, to determine the location of a vessel, that the marine chronometer solved.

Long before that, the use of astronomical tables, specifically of Jupiter's moons, allowed longitude to be measured with sufficient accuracy on land.

The relevant posts have been corrected.

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