Lunar Distances

Lunar distances are measurements of the space between the Moon and specific points on Earth or the Sun, used historically to determine a ship's precise longitude. Navigators observed the Moon’s position relative to stars or the Sun, then compared these observations to predicted tables. Since the Moon’s orbit changes predictably, these measurements allowed sailors to accurately pinpoint their location at sea before modern GPS technology. The process required careful observation, calculations, and understanding of lunar cycles, making lunar distances an essential tool in safe maritime navigation up until the 19th century.