This is an astronomical clock made by Song I-yeong, who was an astronomy professor in 1669 (the year of King Hyeonjong of Joseon). The diameter of the clock is 40cm, and the circumference of the terrestrial globe positioned in the center is about 8.9cm. This clock works by the movements of 2 weights. One rotates the wheel and the toothed wheels to show the time. The other one is to ring the bell. Several metal beads roll down to the inside of the eaves trough, hits the hammer that rings the bell, thereby making it possible for the bell to ring. Metal beads are put up by large, flat wooden spoons, attached to the spokes of the rotating wheels, making this function repeated. In other words, by connecting the two parts of the clock device, in which various saw-toothed wheels move according to the motive power of two weights, and the celestial globe, which has installed in it a terrestrial globe, it has made it possible to know the time and the location of the universe. This celestial globe clock has been highly valued as an independent and creative astronomical clock in the history of the world's clock-making technology history, due to the point that a very new astronomical clock model was made by harmonizing the clock device which had as it motive power the going round of the wheel of a spinning wheel, which was a traditional model during the Joseon Dynasty beginning with King Sejong, and the principles of the alarm clock, a Western-type machine clock. It is known to have been installed at Hongmungwan and used for measuring time and for educational purposes in the discipline of astronomy. It is the only relic remaining among the astronomical clocks made during the Joseon Dynasty.