Sextant

A **sextant** is an instrument used to measure the angle between the horizon and a celestial body, such as the Sun, Moon, or stars. By determining this angle, it is possible to calculate latitude and longitude. The device consists of a graduated arc, marked in degrees, with a movable arm pivoted at the center of the arc. A mirror is mounted on this arm, while a telescope, fixed rigidly to the framework, is aligned with the horizon. To take a reading, the radial arm is adjusted until the celestial body is reflected in a half-silvered mirror, appearing to coincide with the horizon when viewed through the telescope. The angular distance between the celestial body and the horizon is then read from the sextant's scale. One of the earliest precursors to the sextant was the latitude hook, an invention of the Polynesians. This device could only be used to navigate between locations at the same latitude. The hook served as a frame for Polaris, the North Star, a fixed celestial body that helped guide navigation.