• Journal of Astronomy and Space Sciences
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• 제32권1호
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• pp.51-62
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• 2015

I investigated a method for drawing the star chart in the planisphere Cheonsang-yeolcha-bunyajido. The outline of the star chart can be constructed by considering the astronomical information given in the planisphere alone and the drawing method described in Xin-Tangshu; further the chart can be completed by using additional information on the shape and linking method of asterisms out of an inherited star chart. The circles of perpetual visibility, the equator, and the circle of perpetual invisibility are concentric, and their common center locates the Tianshu-xing, which was defined to be a pole star in the Han dynasty. The radius of the circle of perpetual visibility was modified in accordance with the latitude of Seoul, whereas the other circles were drawn for the latitude of $35^{\circ}$, which had been the reference latitude in ancient Chinese astronomy. The ecliptic was drawn as an exact circle by parallel transference of the equator circle to fix the location of the equinoxes at the positions recorded in the epitaph of the planisphere. The positions of equinoxes originated from the Han dynasty. The 365 ticks around the boundary of the circle of perpetual invisibility were possibly drawn by segmenting the circumference with an arc length instead of a chord length with the ratio of the circumference of a circle to its diameter as accurate as 3.14 presumed. The 12 equatorial sectors were drawn on the boundary of the star-chart in accordance with the beginning and ending lodge angles given in the epitaph that originated from the Han dynasty. The determinative lines for the 28 lunar lodges were drawn to intersect their determinative stars, but seven determinative stars are deviated. According to the treatises of the Tang dynasty, these anomalies were inherited from charts of the period earlier than the Tang dynasty. Thus, the star chart in Cheonsang-yeolcha-bunyajido preserves the old tradition that had existed before the present Chinese tradition reformed in approximately 700 CE. In conclusion, the star chart in Cheonsang-yeolcha-bunyajido shows the sky of the former Han dynasty with the equator modified to the latitude of Seoul.

• 천문학회지
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• 제56권2호
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• pp.201-212
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• 2023

The inscription of Cheonsang Yeolcha Bunyajido (天象列次分野之圖) has the sun's locations at the equinoxes, which must have been copied from the astronomical treatises in Chinese historical annals, Songshu (宋書) and Jinshu (晉書). According to the treatises, an astronomer Wang Fan (王蕃, 228-266 CE) referred those values from a calendrical system called Qianxiangli (乾象曆, 223 CE), from which it is confirmed that it adopted the sun's location at the winter solstice of the $(21{\frac{1}{4}})^{th}$ du of the 8th lunar lodge Dou (斗) as the reference direction for equatorial lodge angles. This indicates that the sun's locations at equinoxes and solstices in the calendrical system are the same as those in Jingchuli (景初曆, 237 CE). Hence, we propose that the sun's location at the autumnal equinox in Cheonsang Yeolcha Bunyajido should be corrected from 'wu du shao ruo' (五度少弱), meaning the $(5{\frac{1}{6}})^{th}$ du, to 'wu du ruo' (五度弱), meaning the $(4{\frac{11}{12}})^{th}$ du, of the first lunar lodge Jiao (角), as seen in Jingchuli. We reconstruct the polar coordinate system used in circular star charts, assuming that the mean motion rule was applied and its reference direction was the sun's location at the winter solstice. Considering the precession, we determined the observational epoch of the sun's location at the winter solstice to be t_o = -18.3 ± 43.0 adopting the observational error of the so-called archaic determinatives (古度). It is noteworthy that the sun's locations at equinoxes inscribed in Cheonsang Yeolcha Bunyajido originated from Houhan Sifenli (後漢 四分曆) of the Latter Han dynasty (85 CE), while the coordinate origin in the star chart is related to Taichuli (太初曆) of the Former Han dynasty (104 BCE).

• 천문학회보
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• 제37권1호
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• pp.52.1-52.1
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• 2012

It is often said that there is little geometrical mind in Korean history. However, a method to project the surface of a sphere onto 2-dimensional plain was applied to the representative Korean star chart or Cheonsang Yeolcha Bunyajido (天象列次分野之圖). The method, called the equi-distant polar projection, was explained in detail in ancient Chinese history book of the Tang dynasty, which was originated from older history. Another method of the Mercator projection was introduced by the famous engineer Su Song (蘇頌) of the Song dynasty. The description has quite geometrical thoughts, especially the concept of infinity or convergence appears, However, this type of sky projection method was not widely used in east Asia. When the European Jesuits came to China to evangelize the Chinese people, they found that the Chinese people paid much attention to advanced European astronomical knowledge. Thus, they introduced the European astronomical knowledges into China, and the star chart was one of them. The projection method of the new charts were quite different from the Chinese tradition. When the Koreans brought those new star chart from China, they must have known the geometrical description of the method. The method was described in detail in a volume of Chongzhen Lishi (崇禎曆書) or Xiyang Xinfa Lishu (西洋新法曆書). The explanation consists of three part. One is the quantitative way; another is a geometrical way using axiomatic systems; and the other is the practical method to draw star chart with the geometical projection. However, when we see the Honcheon Jeondo (渾天全圖) that is thought to be duplicated by Kim Jeongho (金正浩), the new geometrical method was not so widely known to the Koreans. I will discuss the reason why the geometrical minds have not been widely adopted in the Korean civilization.

• Journal of Astronomy and Space Sciences
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• 제32권1호
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• pp.63-71
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• 2015

During the reign of King Sejong (世宗, 1418-1450) in the Joseon Dynasty, there were lots of astronomical instruments, including miniaturized ones. Those instruments utilized the technical know-how acquired through building contemporary astronomical instruments previously developed in the Song(宋), Jin(金), and Yuan(元) dynasties of China. In those days, many astronomical instruments had circles, rings, and spheres carved with a scale of 365.25, 100, and 24 parts, respectively, on their circumference. These were called the celestial-circumference degree, hundred-interval (Baekgak), and 24 direction, respectively. These scales are marked by the angular distance, not by the angle. Therefore, these circles, rings, and spheres had to be optimized in size to accomodate proper scales. Assuming that the scale system is composed of integer multiples of unit length, we studied the sizes of circles by referring to old articles and investigating existing artifacts. We discovered that the star chart of Cheonsang yeolcha bunyajido was drawn with a royal standard ruler (周尺) based on the unit length of 207 mm. Interestingly, its circumference was marked by the unit scale of 3 puns per 1 du (or degree) like Honsang (a celestial globe). We also found that Hyeonju ilgu (a equatorial sundial) has a Baekgak disk on a scale of 1 pun per 1 gak (that is an interval of time similar to a quarter). This study contributes to the analysis of specifications of numerous circular elements from old Korean astronomical instruments.