← all shorts

Concept

lunar distances

A circular diagram with a detailed compass-like layout shows the moon at its center, surrounded by numbered divisions and a star in the upper left corner, illustrating lunar distances as an astronomical method for determining longitude.

An astronomical method of finding longitude by measuring the angle between the Moon and a chosen star or the Sun, then comparing the observation against pre-computed tables of where the Moon should be, at known Greenwich times, on a given date. Workable but laborious — a single fix required four hours of calculation — it was the chronometer's main competitor through the late eighteenth century.

Mentioned in 2 articles