• Journal of The Korean Astronomical Society
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• v.29 no.spc1
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• pp.401-402
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• 1996

• Publications of The Korean Astronomical Society
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• v.31 no.3
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• pp.77-85
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• 2016

We study the manufacturers of the astronomical instruments invented as part of the so-called Ganui-Dae (astronomical platform) project in the reign of King Sejong (1418-1450) of the Joseon dynasty. The main purpose of this project was to compile the Chiljeongsan-Naepyeon, a Korean calendar, that lasted for 5.5 years from 1432 to 1438. Through this project, a total of 17 astronomical instruments such as the armillary sphere, celestial globe, and auto-striking clepsydra were developed. It is generally known that most of them were manufactured by Lee Cheon (李蕆, 1376-1451) and Jang Yeong-Sil (蔣英實, fl. 1423-1442). In this study, we investigate the accounts of the Veritable Records of King Sejong, Munjong, and Sejo, focusing on the inscription written out to memorize the completion of the Ganui-Dae project. We found that at least 12 persons took part in manufacturing the astronomical instruments of the Ganui-Dae project. Lee Cheon was involved in the production of four instruments, while Jang Yeong-Sil was involved in two; therefore, it seems that the achievement of Jang Yeong-Sil was overestimated. We also found that Jeong Cho (鄭招, ?-1434) was a scientist and Lee Cheon was an engineer in the early phase of the Ganui-Dae project, while King Sejong and Yi Sun-Ji (李純之, 1406-1465) played major role in the late phase. According to our study, King Sejong and Yi Sun-Ji were involved in the production of at least seven and five instruments, respectively. In conclusion, we believe that this study will be helpful to understand the practical manufacturers of the astronomical instruments invented during the Ganui-Dae project in the Joseon dynasty.

• Publications of The Korean Astronomical Society
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• v.27 no.3
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• pp.61-69
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• 2012

The Ganui (簡儀, simplified armillary sphere) is a representative of astronomical instruments in Joseon Dynasty of Korea, as well as Yuan Dynasty and Ming Dynasty of China. In early 15th century, Joseon's scientists and engineers uniquely developed the Soganui (小簡儀, small simplified armillary sphere) and the Ilseongjeongsiui (日星定時儀, sun-and-star time determining instrument) from the structural characteristic of Ganui. These two astronomical instruments had a new design by the miniaturization and felt convinced a similar performance of Ganui in the harmony with Korean Astronomy and Astrology Cultures. Since mid-18th century after the enforcement of shixian-li (時憲曆), the Soganui and Ilseongjeongsiui handed over the Jeokdogyeongwiui (赤道經緯儀, equatorial armilla) by a change of the observational framework such as the time and angle measures. The Jeokdogyeongwiui made by Gwansanggam (觀象監, Bureau of Astronomy in Joseon Dynasty) adopted the new observational framework. We studied the structural characteristics and scientific values of these 3 astronomical instruments with theirs observation methods.

• Publications of The Korean Astronomical Society
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• v.26 no.3
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• pp.115-127
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• 2011

Since the thirteenth century, large scale facilities and various instruments for astronomical observation were built and installed in East Asia. During the Yuan Dynasty, S. ti.ntai (Beijing astronomical observatory in the Yuan Dynasty, 司天臺) was built in Beijing in 1279. Various astronomical instruments, including Ganui (Jianyi, simplified armillary sphere, 簡儀), Yang-yi (upward hemisphere, 仰儀) and Gyupyo (gnomon, 圭表) were installed in this observatory. These astronomical instruments were modified and improved by researchers of the Joseon Dynasty. Ganuidae (Joseon astronomical observatory, 簡儀臺) was built in Gyeongbokgung (or Gyeongbok palace, 景福宮), Seoul. Its scale was 31 Cheok (Korean feet in the Joseon Dynasty, 尺) in height, 47 Cheok in length and 32 Cheok in width. Lee, Cheon (李蕆, 1376~1451), a responsible leader of Ganuidae project, set up various astronomical instruments with his colleagues. Ganui and Jeongbangan (direction-determining board, 正方案) were installed at the top of this observatory. Gyupyo was installed at the west side of this observatory and Honui (armillary sphere, 渾儀) and Honsang (celestial globe, 渾象) were installed in a small pavilion which was located next to Gyupyo. A decade after installation, this observatory was moved to the north-west side of the palace but almost destroyed during Japanese invasion of Korea in 1592 except Ganuidae. We have analyzed documents about Ganuidae and investigated Chinese remains of astronomical observatories and artifacts of astronomical instruments. In this paper, we suggest the appearance, structure, arrangement and scale of Ganuidae, which are expected to be used for the restoration of Ganuidae at some day in the near future.

• Journal of The Korean Astronomical Society
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• v.29 no.spc1
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• pp.403-404
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• 1996

This paper describes a plan of a new IR phace-shfting interferometric system for testing astronomical aspheric mirror which has big departure from the best fit reference sphere during fine grinding. In this experimental system, some new technology will be adopted. The accuracy of system can reach $\lambda$/40($\lambda$=10.6${\mu}m$)

• Journal of Astronomy and Space Sciences
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• v.32 no.1
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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.

• Journal of Astronomy and Space Sciences
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• v.34 no.1
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• pp.45-54
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• 2017

This study examines the scale unique instruments used for astronomical observation during the Joseon dynasty. The Small Simplified Armillary Sphere (小簡儀, So-ganui) and the Sun-and-Stars Time-Determining Instrument (日星定時儀, Ilseong-jeongsi-ui) are minimized astronomical instruments, which can be characterized, respectively, as an observational instrument and a clock, and were influenced by the Simplified Armilla (簡儀, Jianyi) of the Yuan dynasty. These two instruments were equipped with several rings, and the rings of one were similar both in size and in scale to those of the other. Using the classic method of drawing the scale on the circumference of a ring, we analyze the scales of the Small Simplified Armillary Sphere and the Sun-and-Stars Time-Determining Instrument. Like the scale feature of the Simplified Armilla, we find that these two instruments selected the specific circumference which can be drawn by two kinds of scales. If Joseon's astronomical instruments is applied by the dual scale drawing on one circumference, we suggest that 3.14 was used as the ratio of the circumference of circle, not 3 like China, when the ring's size was calculated in that time. From the size of Hundred-interval disk of the extant Simplified Sundial in Korea, we make a conclusion that the three rings' diameter of the Sun-and-Stars Time-Determining Instrument described in the Sejiong Sillok (世宗實錄, Veritable Records of the King Sejong) refers to that of the middle circle of every ring, not the outer circle. As analyzing the degree of 28 lunar lodges (lunar mansions) in the equator written by Chiljeongsan-naepyeon (七政算內篇, the Inner Volume of Calculation of the Motions of the Seven Celestial Determinants), we also obtain the result that the scale of the Celestial-circumference-degree in the Small Simplified Armillary Sphere was made with a scale error about 0.1 du in root mean square (RMS).

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.11a
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• pp.707-710
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• 1996

During King Sejong's reign in early Chosen Dynasty, the Korean science had been in full bloom. Among the many splendid achievements of the period, though most of them are not extant, astronomical instruments and clocks made for equipping the Royal Observatory are taken as typical works that reflect the characteristics of the King's scientific projects and discussed in the view point that what and how much a well-planned drive and a future-oriented leader can accomplish.

• Journal of The Korean Astronomical Society
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• v.38 no.2
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• pp.117-120
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• 2005

Current instrumentation activities and the open user status of Okayama Astrophysical Observatory (OAO) are reviewed. There are two telescopes in operation and one telescope under reforming at OAO. The 188cm telescope is provided for open use for more than 200 nights in a year. The typical over-subscription rate of observation proposals for the 188cm telescope is ${\~}$ 1.5 - 2. The 50cm telescope is dedicated to $\gamma$-ray burst optical follow-up observation and is operated in collaboration with Tokyo Institute of Technology. The 91cm telescope will become a new very wide field near-infrared camera in two years. The high-dispersion echelle spectrograph (HIDES) is the current primary instrument for the open use of the 188cm telescope. Two new instruments, an infrared multi-purpose camera (ISLE) and an optical low-dispersion spectrograph (KOOLS), are now under development. They will be open as common use instruments in 2006.

• The Bulletin of The Korean Astronomical Society
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• v.42 no.1
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• pp.57.2-57.2
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• 2017

Remote and robotic telescopes are the most effective instrument for astronomical survey projects. The system is based on the dynamic operation of all astronomical instruments such as dome and telescope control system (TCS), focuser, filter wheel and data taking camera. We adopt the ASCOM driver platform to control the instruments through the integrated software. It can convert different interface libraries from various manufacturers into a uniform standard library. This allows us to effectively control astronomical instruments without modifying codes. We suggest a conceptual design of software for automation of a small telescope such as the new wide-field 0.25m telescope at McDonald Observatory. It can also be applied to operation of multi-telescopes in future projects.