In the context of Prague astronomical clock, discuss the Zodiacal ring of the Astronomical dial.
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 signs are shown in anticlockwise order. In the photograph accompanying this section, the Sun is currently moving anticlockwise from Cancer into Leo.
The displacement of the zodiac circle results from the use of a stereographic projection of the ecliptic plane using the North pole as the basis of the projection. This is commonly seen in astronomical clocks of the period.
The small golden star shows the position of the vernal equinox, and sidereal time can be read on the scale with golden Roman numerals. The zodiac is on the 365-tooth gear inside the machine. This gear is connected to the Sun gear and the Moon gear by a 24-tooth gear.
zodiac sidereal time Leo Cancer Zodiac Roman numerals vernal equinox stereographic projection Sun astronomical clock Moon ecliptic