What is the function of the astrolabe?

The "astrolabe" is used to find time, the transit of stars at a certain moment, the time of sunrise and sunset, etc. The heavy plate below is a fixed silver plate, that is, the Polaris plate, which is engraved with latitude and longitude lines, with the north pole as the center and carved around the edge of the plate for twelve hours. The heavy plate on it is a rotatable silver-plated hollow plate, and the small circle is the zodiac, which is engraved with the zodiac. The names of the zodiac in this astrolabe are all engraved with the names of the 12 o'clock in China corresponding to the western zodiac. The hollow disc is engraved with the name and degree of the star, and the center is equipped with a cursor.