• Journal of Astronomy and Space Sciences
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• v.34 no.2
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• pp.161-170
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• 2017

In this study, the characteristics of a horizontal sundial from the Joseon Dynasty were investigated. Korea's Treasure No. 840 (T840) is a Western-style horizontal sundial where hour-lines and solar-term-lines are engraved. The inscription of this sundial indicates that the latitude (altitude of the north celestial pole) is $37^{\circ}$ 39', but the gnomon is lost. In the present study, the latitude of the sundial and the length of the gnomon were estimated based only on the hour-lines and solar-term-lines of the horizontal sundial. When statistically calculated from the convergent point obtained by extending the hour-lines, the latitude of this sundial was $37^{\circ}$ $15^{\prime}{\pm}26^{\prime}$, which showed a 24' difference from the record of the inscription. When it was also assumed that a convergent point is changeable, the estimation of the sundial's latitude was found to be sensitive to the variation of this point. This study found that T840 used a vertical gnomon, that is, perpendicular to the horizontal plane, rather than an inclined triangular gnomon, and a horn-shaped mark like a vertical gnomon is cut on its surface. The length of the gnomon engraved on the artifact was 43.1 mm, and in the present study was statistically calculated as $43.7{\pm}0.7mm$. In addition, the position of the gnomon according to the original inscription and our calculation showed an error of 0.3 mm.

• Publications of The Korean Astronomical Society
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• v.28 no.3
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• pp.55-63
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• 2013

Gyupyo (圭表, Gnomon) consists of Gyu (圭, Measuring Scale) and Pyo (表, Column), and was one of the traditional astronomical instruments in East Asia. Daegyupyo (Large Gnomon) was manufactured in the Joseon dynasty around 1434 ~ 1435. To increase the measurement accuracy, it was equipped with a Hoengyang (橫梁, Cross-bar) and used a Youngbu (影符, Shadow-Definer) which was invented during the Yuan dynasty (1271 ~ 1368). The cross-bar was installed on the top of the column and this structure was called Eol. In addition, three plumbs hanging from the cross-bar was employed to vertically built Eol on the measuring scale. This method was also used to not only check the vertical of Eol but also diagnose the horizontal of the cross-bar. Throughout this study, we found that a cross-bar in a gnomon has played three important roles; measurement of the shadow length made by the central part of the Sun, increase of the measurement precision using the shadow-definer, and diagnosis of the vertical of Eol and the horizontal of the cross-bar itself using the three plumbs. Hence, it can be evaluated that the employment of a cross-bar and a shadow-definer in a gnomon was a high technology in the contemporary times. In conclusion, we think that this study is helpful for understanding the Large Gnomon of the Joseon dynasty.

• Publications of The Korean Astronomical Society
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• v.26 no.3
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• pp.129-140
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• 2011

In this paper, we have studied Sogyupyo (小圭表, small noon gnomon) of the Joseon dynasty. According to the Veritable Records of King Sejong (世宗, 1418 - 1450), Daegyupyo (大圭表, large noon gnomon) with a height of 40-feet [尺] was constructed by Jeong, Cho (鄭招) and his colleagues in 1435, and installed around Ganuidae (簡儀臺, platform of Ganui). On the contrary, the details of Sogyupyo are unknown although the shadow length measurements by Daegyupyo and Sogyupyo are found on the Veritable Records of King Myeongjong (明宗, 1545 - 1567). By analysing historical documents and performing experiments, we have investigated the construction details of Sogyupyo including its development year, manufacturer, and installation spot. We have found that Sogyupyo would be manufactured by King Sejong in 1440 and placed around Ganuidae. And Sogyupyo would be five times smaller than Daegyupyo, i.e., 8-feet. On the basis of experiments, we suggest that although it is smaller, Sogyupyo was equipped with a bar [橫梁] and a pin-hole projector [影符] like Daegyupyo in order to produce the observation precision presented in the Veritable Record of King Myeongjong.

• Journal of Astronomy and Space Sciences
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• v.23 no.3
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• pp.289-302
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• 2006

For a reconstruct draft of the Gyupyo (Gnomon) in King Sejong Era, we collected a lot of documents of the Chosen Dynasty. With the result we made a reduced model by 1/10 and drawing set for the Gnomon in Sejong Era. It is composed of the Gyu, Yongpyo, Hoengryang (a beam), Yeongbu and granitic prop. You can read the scale where the shadow of vertically-standing stick touches the horizontal Gyu. A Shadow-Define. (Yeongbu) was used to focus the shadow cast by the sun's center, measuring the (gnomon) shadow length precisely. A Yeongbu is made of a leaf of copper in the middle of which is pierced a pin-hole for the tiny optical image of the sun which tilted to face the incident sunlight, used the principle of the a pin-hole camera and Scheimplug principle.

• Publications of The Korean Astronomical Society
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• v.27 no.2
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• pp.29-37
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• 2012

In this paper, we study the structure of the Daegyupyo (大圭表, Large Gnomon) of the early Joseon dynasty. A Gyupyo (圭表, Gnomon that is Guibiao as pronounced in Chinese) is composed of a Pyo (表, Biao as pronounced in Chinese) making a shadow and a Gyu (圭, Gui as pronounced in Chinese) measuring its length. It is known that the Daegyupyo with the 40-feet height was constructed between the sixteenth to seventeenth year of the King Sejong reign (1444 - 1445) on the basis of the record of Yuanshi (元史, the History of the Yuan Dynasty). By analyzing historical documents such as Joseonwangjosillok (朝鮮王朝實錄, the Annals of the Joseon Dynasty), Yuanshi, and Jegaryeoksangjip (諸家曆象集, a work written by Sunji Lee), we found a possibility that the Ji (池, a pond) on the Gyu was located in the north side of the Pyo. This structure is different from that in previous studies, but is in a good agreement with that of the 40-feet Guibiao remaining in Dengfeng (登封) of China. Regarding to the Hoengyang (橫梁, cross-bar), we suggest that it was set up by double 5-feet supporting arms apart from the north tip of the Pyo in the radial direction. The 3:4:5 ratio in a rectangular triangle was used to place the Heongyang on the top of the Pyo at a distance of 4-feet (3-feet) in the vertical (horizontal) direction. We also discuss the structural problem when the Hoengyang is positioned apart from the top of the Pyo by supporting arms. In conclusion, we think that this study should be useful in restoring the Daegyupyo of the Joseon dynasty.

• Bulletin of the Korean Space Science Society
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• 1998.10a
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• pp.32-32
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• 1998

No Abstract.See Full-text

• 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.41 no.1
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• pp.51.4-52
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• 2016

이 논문에서는 "원사" "천문지" <경부>조의 기록을 바탕으로 조선시대 영부에 대해 연구하였다. 조선에서는 1435년과 1440년에 처음으로 대규표와 소규표가 제작되었으며, 이들은 모두 횡량을 가진 진화된 형태의 규표로써 영부를 사용하여 그림자길이를 측정하였다. 영부는 바늘구멍 장치로 Needham et al.에 의해 처음으로 그 모델이 제시되었지만, 구조적 측면에서 "원사"의 원문 내용과 차이를 보이고 있다. 이 연구에서는 조선시대 영부를 "원사"의 경부와 동일했을 것으로 가정하였으며, 이를 토대로 새로운 모델을 제시하였다. 바늘구멍을 통과하는 빛의 경로에 대한 분석을 통해 새 모델의 재원 중 "원사"에 명시되지 않은 영부 밑받침의 높이를 추정하였다.

• 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.

• Journal of Astronomy and Space Sciences
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• v.30 no.4
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• pp.299-305
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• 2013

Ganui-Dae, built in the reign of King Sejong, Joseon Dynasty, is a comprehensive observatory. It has various instruments for observation and time signal such as Ganui, Gyupyo(Gnomon), water-hammering type Honui and Honsang, and so on. Studying on Ganui-Dae has been focused on its location, history, criterion, etc, so far. However, studying on its external form and construction method has been conducted insufficiently. This study suggests the model for restoration of Ganui-Dae. The model is based on the analysis about external form of Ganui-Dae in various antique maps, and its construction method in those days.