The Comparison between Calculation Methods on the Solar Position in the Chiljeongsan Naepion and Chiljeongsan Oepion
The Chiljeongsan Naepion (七政算內篇) and the Chiljeongsan Oepion (七政算外篇), landmark achievements in the field of astronomical calendars in Korea, were published in the 26th year (1444 A.D.) of the reign of King Sejong (世宗, 1418-1450 A.D.) of the Choseon(朝鮮) dynasty, firmly establishing the calendar making system of Choseon. The Chiljeongsan Naepion adopts the conventions of the Shoushi calendar (授時曆) of the Yuan (元) dynasty (1280-1367 A.D.) of China, but also consults the Datong calendar (大統曆) and the modified Datong-li Tongkue (大統曆通軌), published during the Ming(明) dynasty (1368-1643 A.D.) of China. Furthermore, the Chiljeongsan Naepion corrects errors in the referred Chinese calendars and adds calculations of sunrise and sunset at the latitude of Seoul. On the other hand, the Chiljeongsan Oepion adopts the conventions of the Huihui calendar (回回曆) of Arabia translated and edited by the Arabian astronomer Mashayihei (馬沙亦黑)  in China. The Huihui calendar uses an Islamic theory of epicycles for its treatment of lunar and planetary motions. This means that aspects of the Ptolemaic system had been introduced into the Korean astronomy in the 15th century The calendar of the Choseon dynasty was made by the method of Chiljeongsan Naepion, but the calculations of solar and lunar eclipses and five planet’s positions are compared to those of the Chiljeongsan Oepion. In this paper, we discussed mainly the differences of the calculation methods of the solar positions in both calendars.
Kwang Hwa Chung, Yong Hyeon Shin, Sue-Nie Park, Hyun Sook Cho, Soon-Ae Yoo, Byung Joo Min, Hyo-Suk Lim and Kyung Hwa Yoo
Y.S. Ahn and E.H. Lee, "The Comparison between Calculation Methods on the Solar Position in the Chiljeongsan Naepion and Chiljeongsan Oepion ", Key Engineering Materials, Vols. 277-279, pp. 824-830, 2005