Copper gold-plated astrometer

[Copper gold-plated astrometer]

Copper gold-plated astrometer, clear, 100 cm high, and 50 cm in diameter. The old collection of the Qing Palace
The instrument carves the equator and the ecliptic on a large copper gold-plated celestial sphere with a diameter of 50 cm, and carves 24 solar terms and stars along the ecliptic. All stars are marked by one to six stars. The two ends of the celestial rotation axis are the north and south poles of the celestial sphere, and the time dial is set at the north pole (now lost). The ball can rotate around this axis, and one rotation represents the Sunday movement of the celestial sphere. There are meridian circle and horizon circle outside the ball. There is scale and orientation in the horizon circle, and a vernier is placed on it; The meridian circle is carved with four quadrants. The astrometer uses the ecliptic coordinates
This astrometer has the function of finding the time of the mid-heaven of a certain star at a certain solar term. The operation method is to first turn a solar term on the spherical surface to the lower part of the meridian circle, then align the cursor on the time plate to the north-south direction, and finally turn a star to the lower part of the meridian circle
There are 60 items in the usage of astrometer according to the Lingtaiyi Imagery, mainly including the conversion of ecliptic coordinates, equatorial coordinates and horizon coordinates and the calculation of time.