An azimuth circle is a device used for measuring the azimuth of celestial bodies. It is used in navigation and astronomy to determine the position of stars and other celestial objects. The term "azimuth circle" is sometimes used interchangeably with "circumferentor" or "surveyor's compass". Other synonyms for this device include "altitude and azimuth instrument", "altitude-azimuth circle", and "navigational instrument". Some older terms for this device include "plain compass" and "mariner's compass". Regardless of its name, the azimuth circle remains an essential tool for those studying the heavens or navigating the high seas.