• Journal of Astronomy and Space Sciences
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• v.28 no.2
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• pp.143-153
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• 2011

The sundials produced in King Sejong era had the functions of accurate observation instruments and were fabricated in various forms such as Angbuilgu (hemispherical sundial). In this study, we investigated the literature, structural characteristics and principles of Hyeonjuilgu, Cheonpyeongilgu and Jeongnamilgu that were developed in Joseon to have the unique structures. Additionally, the sundials were reviewed in the perspective of technical history by comparing them with the sundials of China. For the restoration of the sundials, we identified the principle in which the light spots and shade of the sun were used, and drew the variations of the altitude and azimuth by the yearly motion of the sun on the Siban on the hemispheric and flat surfaces. Based on these results, we completed the design drawings of the three sundials and proposed the restoration models.

• Journal of Astronomy and Space Sciences
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• v.27 no.2
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• pp.161-172
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• 2010

In this paper, we investigate the sundials made by the Kang Family of Jinju in the later period of the Joseon dynasty in terms of their characteristics, functions and the manufacturing technique. One of the characteristics of these sundials is that the value of polar height (i.e., the latitude of Seoul), the name of manufacturer, 24 seasonal subdivisions and so forth are written on the surface. In particular, polar height is expressed as '$37^{\circ}$ 39' 15"' in all 12 sundials examined in this study. To investigate the manufacturing technology in terms of astronomy, we analyze the positions of gnomon and of the lines corresponding to 24 seasonal subdivisions (season lines) and to each hour (hour lines). To verify the accuracy of the positions, we use a planar projection method. That is, we obtain 2D images of the sundials using a camera or scanner, and compare these with astronomical calculations for the positions of gnomon and season/hour lines. We believe that this method will be very useful for the study of sundials preserved elsewhere.

• The Bulletin of The Korean Astronomical Society
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• v.40 no.1
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• pp.87.2-87.2
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• 2015

국립고흥청소년우주체험센터에서는 1m 반사 망원경의 완성을 눈앞에 두고 있다. 천체 망원경으로 관측을 하기 위해서는 시간과 천구 좌표계의 이해는 필수적이다. 하지만 현재 본 센터에서는 천구의를 활용한 프로그램 이외에는 시간과 좌표계를 다루는 체험 프로그램이 전무한 실정이다. 센터에서는 참가자가 자신의 그림자로 시각을 알 수 있는 지평면 해시계, 센터에서 쓰지 않고 있는 구형 가마솥을 재활용한 앙부일구, 덕흥 천문대 교육동의 벽에 벽면 해시계의 제작 및 설치를 추진하고 있다. 차후 이를 활용한 체험 프로그램을 참가자에게 제공한다면 태양의 겉보기 운동을 통해 시간과 공간에 대한 개념을 쉽게 알려줄 수 있을 뿐만 아니라 우리 민족의 과학적 자긍심을 심어줄 수 있을 것으로 기대한다.

• Journal of Astronomy and Space Sciences
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• v.32 no.4
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• pp.395-401
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• 2015

We investigated the six remaining Yang-cheon-cheoks (量天尺), which were first described in the Veritable Record of King Sukjong (肅宗實錄). These woodblock sundials from Korea are structurally very similar to a Gyupyo (圭表, gnomon) or an altitude sundial and are light, compact, and portable. The front side of a Yang-cheon-cheok has two holes for styluses and several hour-lines. We compared the intervals of the hour-lines from the originating point of the stylus placement on all Yang-cheon-cheoks and found that two of the relics had the same hour-lines using the standard of the unit of 1 chon (寸). These two were actually the same sundial although the physical size was different. In spite of the lack of time accuracy, we hypothesize that various-sized Yang-cheon-cheoks were made and widely distributed throughout the public in the late Joseon Dynasty.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.2
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• pp.52.2-52.2
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• 2016

해시계는 태양의 겉보기 운동을 통해 시간과 좌표계에 대한 이해를 도와주는 도구 중 하나이다. 국립고흥청소년 우주체험센터에서는 지평면 해시계와 수직 해시계를 덕흥 천문대에 설치하였다. 지평면 해시계는 관측자 자신의 그림자로 시각을 알 수 있도록 제작하였다. 관측자가 서는 곳에 아날렘마, 매월 1일의 위치 및 각 절기를 표기하여 균시차를 보정할 수 있게 하였다. 벽면 해시계는 가로 1.8m, 세로 1.8m 크기로 황동 주물제작하여 정남향으로 설치하였다. 눈금의 간격은 15분이며 균시차 보정은 하지 않았다. 두 해시계 모두 실제 센터의 경도에 맞춰 설계했으며 표준시와 시간차이를 보이게 했다. 지평면 해시계와 수직 해시계는 센터를 찾아오는 방문객에게 과학적 호기심을 일으키는 야외 체험전시물의 역할을 할 수 있을 것으로 기대하며 향후 해시계를 활용한 실험체험 프로그램을 통하여 청소년이 시간과 좌표계의 개념을 쉽고 명확하게 이해하는데 도움을 주고자 한다.

• Journal of Astronomy and Space Sciences
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• v.33 no.3
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• pp.237-246
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• 2016

We analyze the design and specifications of the Sun-and-Stars Time-Determining group of instruments (Ilseong-jeongsi-ui, 日星定時儀) made during the Joseon dynasty. According to the records of the Sejong Sillok (Veritable Records of King Sejong), Sun-and-Stars Time-Determining Instruments measure the solar time of day and the sidereal time of night through three rings and an alidade. One such instrument, the Simplified Time-Determining Instrument (So-jeongsi-ui, 小定時儀), is made without the essential component for alignment with the celestial north pole. Among this group of instruments, only two bronze Hundred-Interval-Ring Sundials (Baekgak-hwan-Ilgu, 百刻環日晷) currently exist. A comparison of the functions of these two relics with two Time-Determining Instruments suggests that the Hundred-Interval-Ring Sundial is a Simplified Sundial (So-ilyeong, 小日影), as recorded in the Sejong Sillok and the Seongjong Sillok (Veritable Records of King Seongjong). Furthermore, the Simplified Sundial is a model derived from the Simplified Time-Determining Instrument. During the King Sejong reign, the Sun-and-Stars Time-Determining Instruments were used in military camps of the kingdom's frontiers, in royal ancestral rituals, and in royal astronomical observatories.

• Journal of Astronomy and Space Sciences
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• v.32 no.1
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• pp.73-80
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• 2015

The Yang-gyeong-gyu-il-ui (兩景揆日儀) is a kind of elevation sundial using three wooden plates. Sang-hyeok Lee (李尙爀, 1810~?) and Byeong-cheol Nam (南秉哲, 1817~1863) gave descriptions of this sundial and explained how to use it in their Gyu-il-go (揆日考) and Ui-gi-jip-seol (儀器輯說), respectively. According to Gyu-il-go (揆日考) there are two horizontal plates and two vertical plates that have lines of season and time. Subseasonal (節候) lines are engraved between seasonal (節氣) lines, subdividing the interval into three equal lines of Cho-hu (初候, early subseason), Jung-hu (中候, mid subseason) and Mal-hu (末候, late subseason); there are 13 seasonal lines for a year, thus resulting in 37 subseasonal lines; also, there are 12 double-hour (時辰) lines for a day engraved on these plates. The only remaining artifact of Yang-gyeong-gyu-il-ui was made in 1849 (the $15^{th}$ year of Heon-jong) and is kept at the Korea University Museum. We have compared and analyzed Yang-gyeong-gyu-il-ui and similar western sundials. Also, we have reviewed the scientific aspect of this artifact and built a replica. Yang-gyeong-gyu-il-ui is a new model enhanced from the miniaturization development in the early Joseon Dynasty and can be applied to the southern part of the tropic line through a structure change.

• Publications of The Korean Astronomical Society
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• v.38 no.1
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• pp.1-12
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• 2023

Numerous Sundials were fabricated during the reign of King Sejong of the Joseon Dynasty. One among them is Jeongnam-Ilgu (the Fixing-South Sundial), where the time can be measured after setting up the suitable meridian line without a compass. We reconstructed the new Jeongnam-Ilgu model based on the records of 'Description of Making the Royal Observatory Ganui (簡儀臺記)' in the Veritable Record of King Sejong. Jeongnam-Ilgu has a summer solstice half-ring under a horizontal ring which is fixed to two pillars in the north and south, and in which a declination ring rotates around the polar axis. In our model, the polar axis matches the altitude of Hanyang (that is Seoul). There are two merits if the model is designed to install the polar axis in the way that enters both the north and south poles and rotates in them: One is that it is possible to fix the polar axis to the declination ring together with the cross-strut. The other is that a twig for hanging weights can be protruded on the North Pole. The declination ring is supposed to be 178 mm in diameter and is carved on the scale of the celestial-circumference degrees on the ring's surface, where a degree scale can be divided into four equal parts through the diagonal lines. In addition, the time's graduation that is drawn on the summer solstice half-ring makes it possible to measure the daytime throughout the year. An observational property of Jeongnam-Ilgu is that a solar image can be obtained using a pin-hole. The position cast by the solar image between hour circles makes a time measurement. We hope our study will contribute to the restoration of Jeongnam-Ilgu.