What is the astronomical observation in Shen Kuo?

Shen Kuo was the first scientist in the world to notice that Polaris was not actually in the North Pole. In order to measure the actual position of Polaris, he observes Polaris with an armillary sphere every day, and draws the sky map of Polaris' position in the sky in the first half of the night, the middle of the night and the last half of the night every day. After three months of intense work, he finally figured out the actual position of Polaris, not in the North Pole, but far away from the North Pole more than once. On the basis of actual observation of the sun, the moon and the five planets, Shen Kuo put forward the idea of completely abolishing the lunar calendar and changing it to the solar calendar, and proposed that the month should be determined by twelve solar terms, with the big moon being 365,438+0 days and the small moon being 30 days.