A Chinese Innovation Based on Western Methods: The Double-Epicycle Solar Model in the Lixiang kaocheng, 1722

摘要

This article attempts to show how an effort was made by Chinese astronomers to improve on the solar model under the auspice of Emperor Kangxi, in circumstances of the merging of Western and Chinese mathematical astronomy. The result of this effort is the Lixiang kaocheng. Different from the eccentric solar model in the previous calendars, Lixiang kaocheng invented a double-epicycle model to describe the solar motion, aiming at bringing computations into agreement with observation. The observational data used for determining the parameters of solar model might be obtained with Tychonic instruments. But it is also possible that these "observational data" might have been derived from Western astronomical tables. Although actual observations did become more accurate, it did not reflect upon the revision of the solar model. The accuracy of the solar model in the Lixiang kaocheng did not increase very much compared with the previous models.