Chapter 3 The heyday of the third quarter

The Song and Yuan dynasties were the heydays of Chinese astronomy.The calendar during this period has the following characteristics: The most promulgated calendars: up to 25.They have their own characteristics. Among them, the time-serving calendar compiled by Guo Shoujing and others has the best performance and has been used continuously for 360 years, reaching the peak of the Chinese calendar. The most accurate data: the length of the regression year and the synodic month value of many calendars are almost the same as the modern theoretical values, and are in the leading position in the world;

The largest number of large instruments: the Song Dynasty had a water transport instrument platform and four large armillary spheres, and Guo Shoujing in the Yuan Dynasty also created Jianyi and Gaobiao.Among them, Su Song's water astronomical instrument platform, which integrates observation, demonstration and time reporting, was the most excellent astronomical instrument in the world at that time; Stellar observations are the most frequent: especially in the 96 years from 1010 AD to 1106 AD, five large-scale star position measurements have been organized successively, with an average of less than 20 years.

The astronomical achievements of the Song and Yuan Dynasties are closely related to the political stability and economic prosperity during this period.