Link to 9 minute Movie of My SL version of the Clock
Where to see and buy in World
How to read the clock
Prague Web Cam, including the clock, silent
Webcam of Clock with sound
He probably cooperated with the astronomer and Charles University professor Johannes Sindel. Born in 1375 in Hradec Krolove (Bohemia), he was the rector of the school at St. Nicholas in the Small Town in Prague from 1406, later he was a teacher of mathematics in Wien, where he studied on the Faculty of Medicine.
After his return to Prague he became professor of astronomy on Charles University. Later, in 1410, he became a doctor of medicine, the rector of Prague University and private physician of the king Wenceslas IV. According to testimony of Tycho Brahe, Sindel also performed valuable astronomical observations.
Sindel's eclipse instrument (or rather a nomogram for demonstration), which is described in treatise, was derived from Wallingford's albion (cf. 'Richard of Wallingford.' An edition of his writings with introductions, English translation and commentary by J.D. North. I-III, Oxford, Clarendon Press 1976).
The Astronomical Clock was repaired and improved by Jan Taborsky in the 16 th century.
The blue part of the dial represents the sky above the horizon, the brown part the sky below it. There are Latin words ORTVS (east) and OCCASVS (west) written above the horizon, and AVRORA (dawn) and CREPVSCVLVM (twilight) below.
There are three circles on the dial, showing different time: the outer circle with Schwabacher numerals shows the Old Czech Time ("Italian Time"), the circle with Roman numbers shows the Central European Time and the inner circle with Arabic numerals shows the "Babylonian Time": the length of an hour differs there according to the season - it is longer in the summer, shorter in the winter. The Prague Astronomical Clock is the only one in the world able to measure it. Furthermore, the little star by the zodiac ring shows the sidereal time.
The first of these gearing the zodiac and the indicator with the asterisk rotates once a sidereal day. The second gears the indicator of the Sun and rotates once a mean solar day. The third gearing the Moon's pointer rotates accordingly with the mean apparent motion of the Moon. The ball, half silvered and half black, rotates every synodic month and displays its phase.