But it was their great astronomer, Ebn Junis, who accomplished the most valuable of all chronometric improvements.
The latitude, chronometric differences of longitude, and magnetic variation, were determined on shore at this southern point.
An extremely accurate clock or other timepiece. Chronometers are used in scientific experiments, navigation, and astronomical observations. It was the invention of a chronometer capable of being used aboard ship, in 1762, that allowed navigators for the first time to accurately determine their longitude at sea.