Letter to the Editor Chinese models of solar and lunar motions in the 13th century

In the 13th century, a new Chinese astronomical calculation was just put to use and it was almost entirely included in the calendar of Shoushi (formulated by Guo Shou-jing and his colleagues, epoch of AD 1281, adopted from AD 1281−1644). This calendar was one of the most famous and accurate in the history of China. The perfectly systematic theoretical models at that time had been developed for thousands of years, such as those for solar and lunar motions. In this paper, these models and their accuracy within their periods of validity are inferred. The results are also compared with contemporary astronomy.