The Astronomical Clock

JAN 01 1410 · 12:00

The Prague Orloj on the south wall of the Old Town Hall, first installed in 1410 by Mikuláš of Kadaň. Place: South wall, Old Town Hall, Staroměstské náměstí Figures: Mikuláš of Kadaň, clockmaker · Jan Šindel, court astronomer of King Wenceslas IV The lower dial is added later (1490s, by Master Hanuš, often confused in legend with the original builder). The upper dial, the astronomical one, dates from 1410. It is the work of Mikuláš of Kadaň, a clockmaker, in collaboration with Jan Šindel, professor of mathematics and astronomy at the still-young Charles University. It shows four times at once: Old Czech time (sunset reset to zero); German hours (the 24-hour clock); Babylonian hours (variable, from sunrise); and sidereal time. The sun and moon ride a zodiac belt. It is the oldest astronomical clock still operating in the world.