This study aims to investigate the influence of the Deung-nu on the Heumgyeonggak-nu, with a particular focus placed on the time-signal system. This research utilized a reproduction of the Deung-nu, which was constructed in China, along with technical data and historical documents for the analysis. The time-signal device of the Deung-nu is composed of four levels. On the fourth (top) level, constellations of the Four Gods (四神) are displayed, while the third level features the Four Gods represented as figures in their four animal forms: a dragon, a tiger, a bird, and a turtle. The second level includes the 12 animal guardians (十二神) and a 100-division scale (百刻), and on the first (bottom) level, there are four musicians (who play the bell, drum, gong, and cymbals) and a time-signal puppet, which indicates the time through a 100-division scale, providing a diverse visual spectacle. The power system applied to the Deung-nu was influenced by the Shui Yun Yi Xiang Tai (水運儀象臺, around 1092) of the Northern Song Dynasty (960–1127), and this method was likely adopted in the Joseon Dynasty’s Heumgyeonggak-nu as well. This study also compared the characteristics of the Yuan Dynasty’s Deung-nu and the Joseon Dynasty’s Heumgyeonggak-nu, focusing on the movement of the Four Gods, the 12 double-hour (十二時辰) and 100-division time system, the waterwheel power system, and their visual and external displays. Through this comparison, this study identified traditional technologies applied to the Joseon Heumgyeonggak-nu, improvements made, and newly developed technologies.

Angbu-ilgu (仰釜日晷) is a scaphe sundial produced during the Joseon dynasty (1392-1910) and passed down several extant in Korea. This study introduces extant Angbu-ilgu in Korea and its origin, development and alteration. Angbu-ilgu were first invented in 1434, the 16th reign of King Sejong (世宗, 1397-1450), by Lee, Sun-Ji (1406-1465) and Kim, Don (1416-1464) as well as King Sejong (hereafter, Sejong Angbu-ilgu). It is known that Sejong Angbu-ilgu were created by referring to the Yangyi (仰儀) of the Yuan dynasty (1271-1368) in China, which was influenced by an Islamic astrolabe. Although no Sejong Angbu-ilgu remain, the existing Angbu-ilgu were made after the 18th century (hereafter, Extant Angbu-ilgu), and six were designated as treasures. One of remarkable characteristics of Sejong Angbu-ilgu is the rotating pin-hole plate installed at the top of the gnomon, which was removed in Extant Angbu-ilgu. In addition, hour lines were drawn on the basis of 100 intervals (刻) system different from 96 intervals system in Extant Angbu-ilgu. In most Extant Angbu-ilgu, on the other hand, the latitude of Hanyang (nowadays, Seoul) is inscribed as 37˚39´15˝ N, which was measured in 1731, by He, Guo Zhu (何國柱), a Chinese astronomer of the Qing dynasty. However, it is unknown whether or not the latitude of Hanyang was inscribed in Sejong Angbu-ilgu, and if so, what value was used. As the finale of a scaphe sundial, portable Angbu-ilgu combining convenience and aesthetic beauty were also crafted in the 19th century, particularly by Kang, Yun (1830-1898) and Kang, Geon (1843-1909).

In the thirteenth century, there were extensive astronomical exchanges between the Islamic world and Mongol Yuan(元) China. Islamic calendrical system based on the Almagest of Ptolemaios was first introduced into Yuan China, and Islamic Jamal al–Din zij was compiled by Jamal al-Din and Muslim astronomers active in Islamic observatory. In Ming(明) China, Chinese-Islamic zij, Huihui-lifa (回回曆法) originated from Jamal al-Din Zij was compiled by the Chinese and Muslim Astronomers, and it was transmitted to Joseon(朝鮮) Korea during the King Sejong period(1418-1450). However, Korean astronomers found the serious mistakes in the epoch and the date conversion method of the Huihui-lifa, and they corrected all the errors and applied newly revised algorithm, and compiled Korean version of Islamic zij, Chiljeongsan-Oepyeon (七政算外篇, 1444). Interestingly however, we find that parallax theory of the zijes originated from Jamal al–Din zij (ie, Jamal al–Din type zij) have a origin from Indian astronomy in 6-7 century. In addition, it is confirmed that there is a difference between the parallax theory of Jamal al–Din type and Theon type zijes (originated from Theon’s handy table). In this study, therefore, we trace the travels of astronomical tables through the comparison of parallax correction methods and tables included in the zijes of Jamal al–Din type and Theon’s type. We discuss on the routes of the parallax theory transmitted from ancient Greece and India to Joseon Korea via Islamic world and China, respectively.