中国古代的视差理论——以日食食差算法为中心的考察

日食食差算法是中国传统日食计算中的核心算法，研究该算法的造术原理及其精度，对评价中国古代日食算法的优劣和精度有重要的参考意义。以各历相关术文为例，进一步阐明日食食差的天文意义，指明食差算法是日食食分算法的一个子算法，食差算法应该是气差、刻差和时差的代数和；在前人的研究基础上，详细讨论中国古代食差算法的沿革史，并根据各时期食差算法的特征，以《宣明历》、《崇天历》、《纪元历》等历法作为关节点，对食差算法的历史进行分期；通过对《宣明历》、《纪元历》和《授时历》等历法中食差算法的精度讨论，证明中国古代食差算法中气差函数和刻差函数的符号选择的正确性，表明中国古代日食食差算法是一个非常优秀的算法。

A Study on Parallax Theory in Ancient China with Shicha Algorithm As an Example

Shicha algorithm is an important algorithm of solar eclipse theory. To explain the method of such an algorithm and its precision is of great significance for us to evaluate objectively the solar eclipse in ancient China. Based on previous researches, this paper illustrates the real meanings of Shicha algorithm, reveals the connection between Shicha and shicha and concludes that shicha algorithm is one part of solar-eclipse-magnitude algorithm. The paper discusses the history of Shicha algorithm and divides the history of Shicha algorithm into several stages according to its characters. It also analyses the precision of Shicha in Xuanming Calendar, Jiyuan Calendar and Shoushi Calendar. The conclusion about the precision of Shicha not only proves that the sign of qicha and kecha is correct, but also points out that the shicha algorithm designed by the ancient Chinese astronomers is an excellent one.