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Su Song Star Map 1, Song dynasty - Public domain old map
Summary
This is a star map for the celestial globe of Su Song (1020-1101), a Chinese scientist and mechanical engineer of the Song Dynasty (960-1279). It was first published in the year 1092, in Su's book known as the Xin Yi Xiang Fa Yao (Wade-Giles: Hsin Yi Hsiang Fa Yao). On this star map there are 14 xiu (lunar mansions) on Mercator's projection. The equator is represented by the horizontal straight line running through the star chart, while the ecliptic curves above it. Note the unequal breadth of the lunar mansions on the map.
Su Song's star maps had the hour circles between the xiu (lunar mansions) forming the astronomical meridians, with stars marked in quasi-orthomorphic cylindrical projection on each side of the equator, and thus was in accordance to their north polar distances. Not until the work of Gerard Mercator in 1569 was a celestial map of this projection created in the Western world (Needham, Volume 4, Part 3, 569).
This picture appears on page 277 of Joseph Needham's book Science and Civilization in China: Volume 3, Mathematics and the Sciences of the Heavens and the Earth.
Traditional Chinese astronomy has a system of dividing the celestial sphere into asterisms or constellations, known as "officials" (Chinese 星官 xīng guān). The Chinese asterisms are generally smaller than the constellations of Hellenistic tradition. The Song dynasty (13th-century) Suzhou planisphere shows a total of 283 asterisms, comprising a total of 1,565 individual stars. The asterisms are divided into four groups, the Twenty-Eight Mansions (二十八宿, Èrshíbā Xiù) along the ecliptic, and the Three Enclosures of the northern sky. The southern sky was added as a fifth group in the late Ming Dynasty based on European star charts, comprising an additional 23 asterisms. The Three Enclosures (三垣, Sān Yuán) include the Purple Forbidden Enclosure, which is centered on the north celestial pole and includes those stars which could be seen year-round, while the other two straddle the celestial equator. The Twenty-Eight Mansions form an ecliptic coordinate system used for those stars visible (from China) but not during the whole year, based on the movement of the moon over a lunar month.
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