Astronomical clock

An astronomical clock, also called a horologium or orloj, is a timepiece built with extra dials and gearing to show the relative positions of the Sun, Moon, zodiac constellations and major planets alongside the time of day. Its clearest ancestor is the second-century BC Antikythera mechanism, a geared bronze device able to track celestial positions and predict eclipses, and Chinese inventor Su Song built a water-driven astronomical clock tower in the eleventh century; medieval European clockmakers such as Richard of Wallingford in the 1330s and Giovanni Dondi dellOrologio in the 1340s to 1360s built the traditions best known masterpieces. A typical astronomical clock adds a twenty-four-hour dial, the zodiac and lunar phase to ordinary timekeeping, and many use dragon hands to track the Moons nodes for eclipse prediction, all built around the old geocentric model with the Earth at the center.