Observational Accuracy of Sunrise and Sunset Times in the Sixth Century China

作     者：Yong Li Yong Li National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012

作者机构：National Astronomical Observatories Chinese Academy of Sciences Beijing 100012 

出 版 物：《Chinese Journal of Astronomy and Astrophysics》 (中国天文和天体物理学报（英文版）)

年 卷 期：2006年第6卷第5期

页      面：629-634页

核心收录：

学科分类：07[理学] 070402[理学-天体测量与天体力学] 0704[理学-天文学] 

基　　金：the Tianyuan Foundation of China(A0324673) 

主　　题：history of astronomy -- astrometry -- solar-terrestrial relations -- methods statistical 

摘      要：The Daye Calendar was compiled in AD 597 in the Sui Dynasty. We investigate the records of sunrise and sunset times on the 24 solar-term days in the calendar. By converting the ancient Chinese time units, Chen, Ke and Fen to hour, minute and second, and carrying out a comparison between the ancient records and values computed with modem astronomical theory, we find that the accuracy of solar measurements in the Sui period is remarkably high： for sunrise times, the average absolute deviation is 3.63 min （this value can be further reduced to 3.03 min when erroneous data are excluded）, and for sunset times it is 3.48 min. We also find that the observed sunrise and sunset times are strictly symmetrically distributed with respect to both the Winter Solstice and the Summer Solstice, with their deviations showing a similar symmetrical distribution as well. We give a discussion on the date of observation, the feature of the data, and possible reasons of the deviation.