An astronomical clock made by Song Yi-yeong, an astronomy professor, in the 10th year of King Hyeonjong of the Joseon Dynasty (1669), it was installed in Hongmungwan and used for time measurement and astronomy teaching.
The diameter of the watch is 40 cm, and the diameter of the globe at the center is about 8.9 cm.
It moves by the motion of two pendulums, one rotates the wheels and cogwheels for vision, and the other is for the bell-beating device. As several iron balls roll down the gutter, the hammer striking the bell is caught and soon the paper This operation is repeated while the iron ball is lifted by the spatulas attached to the spokes of the rotating wheel.
In other words, the clock device that moves various gear wheels by using two axes as power and the two parts of the heavenly body in which the earth is installed are connected, so that the time and the position of the celestial body can be known at the same time.
It is the only remaining relic among the astronomical clocks made in the Joseon Dynasty. It is said that a completely new astronomical clock model was created by harmonizing a clock device powered by the principle of the water wheel, a traditional model of the Joseon Dynasty, and the principle of an alarm clock, a Western mechanical clock. In this respect, it is highly regarded as an original astronomical clock in the history of world watchmaking technology.