Shuiwei (水位)
Authors: Boshun YANG
Shuǐ Wèi (水位, Water Level) is a four-star asterism in the celestial region of the lodge Dōngjǐng (東井, Eastern Well). It belongs to the Shi tradition and can be traced back at least as far as the Han dynasty. Its stars lie in the region of the modern constellations Gemini and Cancer. The extant recension of the Tianwen yaolu (天文要錄, Essentials of Celestial Patterns), quoting the Shishi xingjing (石氏星經, Master Shi’s Star Canon), also records Shuǐchéng (水成, Water Completion) and Shuǐchāng (水昌, Flourishing Water) as alternative names.
Concordance, Etymology, History
The name Shuǐ Wèi literally denotes the height of the water surface in a river, lake, or vessel. The word wèi (位) refers to a position, elevation, or level that can be compared with another. The Kaiyuan zhanjing開元占經 quotes Master Shi as saying:
“The asterism Shuiwei governs shuiheng水衡. When the balance is level, it resembles water: (the waters and) marshes flow onward after reaching an even level and do not become obstructed.” 水位星，主水衡。衡平象水，（水）澤平而後流，澤不壅塞也。
Here, shuiheng (水衡) primarily denotes the administrative charge of regulating waters and controlling their storage and discharge. The expression “balance level” draws on the image of a level measuring instrument and the tendency of water surfaces to seek a level, meaning that after marshes reach an appropriate water level, they drain smoothly and waterways are not obstructed. The passage describes an ideal order in which water levels are measured and waterways properly regulated, rather than the geometrical arrangement of the four stars on a chart.
Traditional Chinese water markers known as shuize (水則), together with other water gauges, provide later but materially visible analogues for this imagery. Beginning in the first year of the Guangde era of the Tang dynasty (763), the stone fish and inscriptions at Baiheliang recorded the low-water levels of the Yangtze River near Fuling by comparing the water surface with fixed markers. UNESCO describes the site as preserving a hydrological record extending over approximately 1,200 years. Another famous example could be the pavilion and stone monument in Ningbo used to measure water level in the Grand Canal, known as the Shuǐzébēi 水則碑 "Water Gauge Stele", of which the base dates to the Southern Song dynasty (c. 1259).
The Huangdi zhan states that Shuiwei “governs the water officials.” In 115 BCE, Emperor Wu of the Han established the office of the Shuǐhéng dūwèi (水衡都尉, Commandant of Water and Parks), which administered Shanglin Park. Its subordinate agencies were also concerned with imperial parks, ponds and marshes, natural resources, and related revenues. Ying Shao explained:
“In antiquity, the official in charge of mountains and forests was called the heng; because he administered the ponds and parks, so the office was called Shuiheng.”古山林之官曰衡，掌諸池苑，故稱水衡。
The establishment of this office was broadly contemporary with the formation of the Shuiwei asterism, suggesting a possible resonance in their administrative terminology. The Shuiwei asterism—or at least the associated imagery of Shuiheng—may also have entered mythological literature. Zhang Heng wrote in his Sixuan fu (思玄賦, Rhapsody on Contemplating the Mystery):
“Ahead, I made Changli sweep the air with its wings; I entrusted Shuiheng to Xuanming.” 前長離使拂羽兮，委水衡乎玄冥。
The rhapsody chiefly describes a celestial journey and refers to numerous asterisms. Xuanming is the deity of water; Shuiheng may be understood concretely as an office of celestial water administration, while possibly also alluding to the four stars of Shuiwei.
Identification of stars
The reconstructions of Shuiwei at different periods proposed by earlier scholars are listed below. Overall, the position and configuration of the asterism remained broadly stable, although the identification of its individual member stars varied slightly. These differences do not necessarily reflect a clear pattern of historical development; some may instead have resulted from occasional errors in stellar identification. Yang Boshun examined eighteen records of the Moon or planets trespassing against Shuiwei between 1079 and 1102. Nine accord with the earlier Han–Jin configuration, while only two accord with the new Jingyou/Huangyou charts; the remaining records do not permit a unique determination. This suggests that, even after new star catalogues had been compiled, practising observers might continue to follow different traditions of stellar identification.
A more conspicuous change occurred in the seventeenth century. When missionaries participated in the reform of Chinese astronomy, they reidentified Chinese asterisms with reference to Bayer’s star atlas. Although the two groups are similar in actual brightness, Bayer’s charts depicted 68 Gem (V = 5.26), f Gem (V = 5.05), and g Gem (V = 4.89) as markedly smaller than the slightly more southerly group comprising 6 CMi (V = 4.55), 11 CMi (V = 5.25), 8 Cnc (V = 5.14), and ζ Cnc (combined V = 4.67). This distorted representation of stellar brightness may have led the missionaries to identify Shuiwei with the latter group.
| Star Names or Orders(Qing) | Han Dynasty (SUN X. & J. Kistemaker[1]) | 3rd to 6th Century (Boshun Yang[2]) | Song Dynaty (Boshun Yang[2], 1034 CE) | Song Dynasty (Pan Nai[3], 1052 CE) | Song Dynasty (Boshun Yang[2], 1052 CE) | Yuan Dynasty (Pan Nai[4], 14th century) | Qing Dynaty (Yi Shitong[5], 18th Century) | Ho PENG YOKE[6] |
|---|---|---|---|---|---|---|---|---|
| 1st | 68 Gem (determinative） | f Gem (determinative） | 68 Gem (determinative） | 68 Gem (determinative） | 68 Gem (determinative） | HIP 36340 | 6 CMi (determinative） | 6 CMi |
| 2nd | f Gem | g Gem | f Gem | f Gem | f Gem | 68 Gem | 11 CMi | 11 CMi |
| 3rd | g Gem | 85 Gem | g Gem | g Gem | g Gem | f Gem | 8 Cnc | 8 Cnc |
| 4th | 85 Gem | μ Cnc | 85 Gem | 85 Gem | 85 Gem | g Gem | ζ Cnc | ζ Cnc |
Maps (Gallery)
| historical map | modern identification | same in Stellarium |
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IAU Working Group on Star Names
In 202x, the name of the historical constellation "xxx" was suggested to be used for one of the stars in this constellation. ...
Decision: ...
References
- ↑ Sun Xiaochun. & Kistemaker J. The Chinese sky during the Han. Leiden: Brill. 1997, Pp241-6.
- ↑ 2.0 2.1 2.2 B.-S. Yang杨伯顺, Zhongguo Chuantong Hengxing Guance Jingdu ji Xingguan Yanbian Yanjiu 中国传统恒星观测精度及星官演变研究 (A Research on the Accuracy of Chinese Traditional Star Observation and the Evolution of Constellations), PhD thesis, (Hefei: University of Science and Technology of China, 2023), Pp297-304.
- ↑ Pan Nai潘鼐. Zhongguo Hengxing Guance shi中国恒星观测史[M]. Shanghai: Xuelin Pree. 1989, Pp220-226.
- ↑ Pan Nai潘鼐. Zhongguo Hengxing Guance shi中国恒星观测史[M]. Shanghai: Xuelin Pree. 2009. p435-443.
- ↑ Yi Shitong伊世同. Zhongxi Duizhao Hengxing Tubiao中西对照恒星图表1950. Beijing: Science Press.1981.
- ↑ P.-Y. Ho, “Ancient And Mediaeval Observations of Comets and Novae in Chinese Sources,” Vistas in Astronomy, 5(1962), 127-225.
