인사동 출토 일성정시의日星定時儀 세 환環의 유물

Abstract

This study investigates the components of the sun-and-stars time-determining instrument (il-seong jeongsiui) of King Sejong's era. These artifacts were excavated in 2021 from the stratum dating back to the 15th and 16th centuries in Insa-dong, Jongno-gu, Seoul. The sun-and-stars time-determining instrument is an astronomical instrument that integrates a sundial and a star- dial. This is one of four of these instruments, all of which were created during the reign of King Sejong (r. 1418-1450). The sun-and-stars time-determining instrument consists of three rings with gradations of the angles and times. These three rings were found fragmented, however, of the three, the star-dial hundred-interval ring and the celestial-circumference degrees-and-fractions ring were able to be fully reconstructed. e diameters and widths of these three concentric rings closely matched the values documented in historical records. Notably, the sundial hundred-interval ring, wedged between the other two, exhibited evidence of rivet-based fixings to ensure the stable support of the other two rings. e retrieval of the celestial-circumference degrees-and-fractions ring is particularly significant, given that no extant rings are engraved with celestial-circumference degrees. The method of inscribing these degrees on a ring had largely been forgotten until this discovery. Both hundred-interval rings feature time scales engraved in a clockwise manner, and the scale for celestial-circumference degrees, corresponding to angles, is similarly carved in a clockwise direction on the celestial-circumference degrees-and-fractions ring. This clockwise orientation of the celestial-circumference degrees aligns with the daily movement of the sidereal time reference. The gradation of the smallest unit among the four layers on the lateral face on all rings consistently appears on the outer section of the rings. Furthermore, both the star-dial hundred-interval ring and the celestial-circumference degrees-and-fractions ring display identical knobs in the shape of the head of Anaruddha. All rings have their gradations inlaid with silver, providing functional elements that enhance the measurement of celestial objects using the sun-and-stars time-determining instrument. According to the literature on this instrument, it was correctly set up by observing the diurnal rotation of the Angular Arranger (α Umi) in the polar-sighting ring at nighttime, and time was measured by monitoring the movement of the Imperial Star (β Umi). The observation method of the sun-and-stars time-determining instrument was also applied to the simplified version of the instrument.