Research On Star Maps In Hengxing Jingwei Tushuo

Hengxing jingwei tushuo is one volume of the astronomical encyclopedia Chongzhen lishu in late Ming China(1629?1644).It consists of 25 pieces of star maps in four different types,all of which generated when the Western astronomy was first introduced to China.This research looks into these star maps and focuses on two questions:How were they illustrated?And how the stars changed if compared with the traditional stars in ancient China?For the first question,we look through texts for clues and then do analysis to inspect them.The results are as follow.Chidao nanbei liangzongxingtu and Huangdao nanbei liangzong xingtu were illustrated with stereographic projection.There are two methods to plot them,both usable and accurate.Jianjie zongxingtu was illustrated with vertical perspective projection,and the projective point locates near the South Pole when the borderline is tangent to the celestial sphere at the circle of perpetual occultation.We demonstrate that the map makers used 36° as the radius of the lower circle,rather than 20° as the authors claimed in the book.Geometric drawing is suitable for this kind of star map.Huangdao ershi fen xingtu were illustrated with sinusoidal projection,and some adjustments were applied to the edges and the ratio of latitudes.In all,these four kinds of star maps indicate the transmission of the Western cartography to China.To study the changes of stars in the map,we visualize the star charts based on Matlab programming,and then compare it with star maps and Chinese traditional star atlas Butiange synchronously,in order to explain the details in the image.The result shows that map makers tried to preserve the original shapes of Chinese traditional constellations especially by adding the "invisible stars" or "stars with no data" into them.To the contrary,some of the traditional constellations were completely abandoned.The contradiction is also reflected in the texts of Hengxing lizhi and Hengxing jingwei tushuo.We infer that lack of acknowledgments to the Western rules of selecting stars may be one of the reasons.