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This quadrant, rotating on a column with holes, was used to determine the altitude of celestial bodies and to measure the angle of the sun. On either end of the arc is a projecting "ear" with midline for the purpose of calibrating. The user could adjust the arc to ensure that the sunlight passed though the minute aperture on the column and accurately projected on the midline of the "ear". Thus, the segment from aperture to the "ear" indicates the direction of the sun, while the difference between the angle marked on the "ear" and the hanging line (which has been lost) is the distance from the zenith to the position of the sun at that time. Thus, 90 degrees minus the difference is the sun's height from the horizon. The compass on the bottom is for adjusting the direction.
Decorated with tendril patterns, this sophisticated instrument is one of the finest technological calculating pieces made by the Qing imperial workshops, and it is included in the book Illustrated Regulations of Ceremonial Paraphernalia of the Qing Dynasty (Huangzhao liqi tushi).