Design description of astronomical clock

The outer ring of most astronomical clocks is a 24-hour hand dial, which repeats from the Roman numeral I( 1) to XII( 12), and then from I( 1) to XII( 12). The current time is indicated by a pointer, which usually has a picture of a golden ball or the sun at the end. Local noon is usually directly above the dial and midnight is directly below the dial. Minute hands are basically not used.

The pointer indicates the azimuth of the sun and the latitude of the horizon. From the azimuth angle, the upper part of the dial indicates the south, and the two VI(6's (6) indicate the east and the west. Seen from the horizon latitude, the zenith is above the dial, and two VI(6) determine the horizontal line. This is designed from the northern hemisphere of the earth. Of course, this design is most accurate at the vernal equinox, that is, when the day and night are equally divided.

If XII( 12) is not above the dial, or the number is in Arabic instead of Roman, the time is displayed as Italian time. In this system, 0 o'clock is the time when the sun sets.

Calendar and Constellation: The year is usually represented by 12 constellations, which are generally arranged in a circle in a 24-hour dial to show the trajectories of the ecliptic, the sun and the planets in the starry sky.

Because of the tilt angle of the earth's rotation, the projection of the ecliptic planet on the clock surface is a little off center and has some slight deformation. The angle of stereo projection is based on the north pole. Usually, the design of the astrolabe is based on the south pole.

The way to determine the date is to determine the current constellation at the intersection of the horoscope. This indicator rotates around the constellation disk within one year, and the sun moves from one constellation to another. Take the dial in Prague as an example. The sun dial is now moved to Aries and Pisces is in the East. So the time is late March or early April.

Moon: There is a circle of numbers on the clock plate from 1 to 29 or 30 indicating the period of the moon: the new moon is 0 and the full moon is 15. The black hemisphere is usually used to indicate the position of the moon.

Hour line: The unequal-length timing method usually divides the day into 12 equal-length hours and divides the night into another 12 hours. In Europe, the days in summer are much longer than the nights, so the days are longer than the nights. Similarly, in winter, the days are shorter than the nights. These unequal hours are represented by the curve in the middle of the clock plate, and the long hours in summer are on the periphery of the plate. Astronomical clock, alias latitude and longitude time controller. It is used in street lamps, advertising lights, architectural lighting and other occasions where the time of turning on and off the lights needs to be changed regularly with the change of sunrise and sunset with the set latitude and longitude.