The Astronomical Dial

The background represents the Earth and the local view of the sky. The blue circle directly in the center represents the Earth, and the upper blue is the portion of the sky which is above the horizon. The red and black areas indicate portions of the sky below the horizon. During the daytime, the sun sits over the blue part of the background and at night it sits over the black. During dawn or dusk, the mechanical sun is positioned over the red part of the background.

Inside the large black outer circle lies another movable circle marked with the signs of the zodiac which indicates the location of the sun on the ecliptic.

The movements of the various mechanical parts of the astronomical dial are too slow to appreciate in real time, but become easier to comprehend using the computer model of Orloj

© E. Shatara, 2008