朝鮮世宗期における 天文儀器の開発と利用

 Sang-Hyeon Ahn (韓國天文硏究院)

2020.12.05. @天文文化研究会

Political transition 

高麗->朝鮮

朝鮮世宗 1397-1450

禮樂制度

The morality was well described by a sentence in a famous Chinese classic called lizi (禮記): 

“大樂與天地同和. 大禮與天地同節,”

which is translated as

“Great music harmonizes with the Nature 

Great rites follows the order of the Nature.”

Here the concept of harmonization is related with politics, and that was realized or demonstrated by ancestral rites 祭祀. Music is an important part in performing rituals 儀式.

Music can unite people!

Moreover, the concept of the order of Nature is realized by an exact definition of seasonal grants 節氣 that is calendar.

Calendar can give public order to the people!

渾儀，渾象，簡儀，小簡儀

日星定時儀：

Its structure consists of three rings on a cross, called the Jucheondo-bunhwan (周天度分環), Ilgubaekgak-hwan (日晷百刻環), and Seonggubaekgak-hwan (星晷百刻環), and it is made based on the altitude (latitude) of the North Pole in Hanyang.

The north and south are ruled by aligning the UMi (勾陳大星，勾陳一) in the outer ring. The stars that appear in the Jeonggeukhwan are compared. Based on 1437 when Ilseongjeongsiui was created, Cheonchusung was considered the North Pole at that time. It is said that Gujin daeseong 勾陳大星is aligned between the outer ring and the inner ring, and Cheonchusung天樞星 is aligned inside the inner ring. Among the constellations of the North Pole at that time, Cheonchusung was considered due north (正北), and Gujin (勾陳), the North Star in today's article, is the closest and brightest star to Cheonchusung, so it was used to align it with the North Pole.

輪之上面, 置三環, 曰周天度分環, 曰日晷百刻環, 曰星晷百刻環。 其周天度分環居外運轉, 外有兩耳, 經二尺、厚三分、廣八分。 日晷百刻環居中不轉, 經一尺八寸四分, 廣厚與外環同。 星晷百刻環居內運轉, 內有兩耳, 經一尺六寸八分, 廣厚與中外環同, 有耳, 所以運也。 三環之上, 有界衡, 長二尺一寸、廣三寸、厚五分。 兩頭中虛, 長二寸二分、廣一寸八分, 所以不蔽三環之畫也。 腰中左右, 各有一龍, 長一尺, 共捧定極環。 環有二。 外環內環之間, 勾陳大星見; 內環之內, 天樞星見, 所以正南北赤道也。 外環經三寸三分、廣三分, 內環經一寸四分半、廣四釐, 厚皆二分, 些少相接如十字。 界衡兩端虛處內外, 各有小穴, 定極外環兩邊亦有小穴, 以細繩通貫六穴而結於界衡之兩端, 所以上候日星, 而下考時刻者也。 周天環, 刻周天度, 每度作四分, 日晷環, 刻百刻, 每刻作六分, 星晷環亦刻如日晷, 但子正過晨前子正, 如周天, 過一度爲異耳。 用周天環之術, 先下水漏, 得冬至晨前子正, 以界衡候北極第二星所在, 以誌輪邊, 仍以周天初度之初當之, 然年久則天歲必差, 以《授時曆》考之, 十六年有奇, 退一分, 六十六年有奇, 退一度, 至是須更候以定之。 北極第二星, 近北辰而最赤明, 衆所易見, 故以之測候耳。

Reference 

Janss kr

Comet c/1723 T1

日星定時儀 naver

Kasi

Wiki