What are the main achievements of astronomy in Tang Dynasty?

In astronomical research, people in the Tang Dynasty also took a more serious attitude. In the early Tang Dynasty, Lv Cai (600 ~ 665) designed a new clepsydra for timing. Li improved the armillary sphere of Luo, Zhang Heng and others and the iron level of the Northern Wei Dynasty, making it a freely rotating Liuhe instrument. In addition, during the reign, Li also compiled the Linde calendar, which determined the new moon according to the real coincidence time of the sun and the moon. The arrangement of months was no longer 29 days and 30 days. According to the Dunhuang Star Map discovered in Dunhuang in the early Tang Dynasty, astronomers at that time studied the star map of the previous generation. This star map (1907 was taken away by the Englishman Stan) marked 1350 stars, which is the largest number of stars in the ancient star map in the world today. However, judging from the accuracy of the position of the stars, the producers probably mainly copied and sorted out the ancient maps, and did not make detailed observations themselves. It should also be mentioned that Li, a great astronomer in the early Tang Dynasty, was also a divination master trusted by Emperor Taizong at that time. He wrote an astrological book Yi Sizhan and a famous book in the history of astronomy, The Book of Jin and Tian Zhi. It is said that he "keeps good or bad luck and is consistent." At that time, the artist suspected that he had other labors, but because of his research, it was impossible to measure them (Old Tang Shu Li Chuan). He even used his clever words and excuses to dissuade Emperor Taizong from a rumored activity of cleaning the so-called "female warrior king" (alluding to Wu Zetian). Li's achievements show that astronomy and astrology went hand in hand in the Tang Dynasty.