Guo Shoujing
It was said that in 1227, the Jin dynasty transferred the ancient astronomical instruments from Kaifeng to the first observatory in Beijing. In 1279, the succeeding Mongols under Kublai Khan built a new observatory just north of the current observatory. Kublai Khan made his chief adviser of hydraulics, mathematics and astronomy, Guo Shoujing, director of the observatory in 1283 after the death of Guo's friend and predecessor Zhang Wenqian. After the Mongols, Zhu Yuanzhang, the founding Ming Emperor, transferred the instruments from Beijing to Nanjing. When the Yongle Emperor came to power, he had craftsmen make copies of the instruments in Nanjing and sent them to the Beijing observatory.