邢云路《戊申立春考证》解析

A Research on Wushen Lichun Kaozheng Written by Xing Yunlu in Ming Dynasty

根据明末邢云路所撰《戊申立春考证》,通过历法推步结果与实测数据的比验,详细考察了邢氏确定明万历三十六年(1608年)立春节气时刻的推演过程.分析了邢氏观测误差约2°的原因.完整给出依《授时历》和《大统历》推步该年的气朔结果,两者仅立春异日.且邢氏实测所得立春时刻=14.912333 d和年长=365.2421 90 d与《授时历》的符合率远优于《大统历》.古代的节气测算方法并不精确,为褒《授时历》贬《大统历》,邢氏有隐匿数据和修改数据之嫌,但实测年长史上最佳亦不排除巧合.给出邢氏为使历法推步结果与实测密合可能所做的数据调整方案,包括历数及观测数据的修改.

The book Wushen Lichun Kaozheng （WLK） was written by Xing Yunlu （XYL）,an astronomer in Ming dynasty （1368-1644）,as recorded that XYL erected up a 60 chi （1 chi is roughly 1/3 meter） gnomon in Lanzhou city to observe the shadow length of the Sun＇s transit,by using the three days＇ data measured by XYL to deduce the time of Lichun,one solar term when longitude =315°,in the 36th year （1608） in the Wanli period （1573-1620）.Based on this fact,we carefully investigate this book,and compare the solar terms in 1608 with those calculated by both calendars of Shoushi Li and Datong Li step by step as according to the texts.The whole calculations and related data are given.The causes of the 2° error observed by XYL are analyzed.We calculate the solar terms in 1608 according to the two calendars,and the 24 results show only Lichun occurred in different days,and the real difference between them is just 0.1 d.By using the three days＇ observations,XYL calculated Lichun=14.912333 d and year length=365.242190 d,the coincidence rate of Shoushi Li is much larger than Datong Li.Ancient method to obtain the time of solar terms from the solar shadows is not accurate enough.In order to approve Shoushi Li and despise Datong Li,we find the clue that XYL possibly hid or even modified the original data.But the fact could not be got rid of that the best tropical year length existed in the history of China measured by him is of coincidence.For the purpose of the results of Lichun derived by both measurements and calendars coming to the same,we give the data adjustment scheme including modifying the data of either calendars or measurements as possibly performed by XYL.