The Astronomical Dial shows the medieval perception of the Universe: the Earth is the center.
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 CPEPVSCVLVM (twilight) below.
There is a Zodiac ring, which represents the stars in the sky and it moves according to it. The two clock hands bear the signs of the Sun and the Moon.
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 (and I can see my camera ist still in Finnish time 6.29AM :-)).