What does the star map in the Book of Destiny refer to? (novel or TV series)

In the TV series "Choose Heaven", Chen Changsheng entered Zhou Garden to find the star map, and the Queen also wanted to find the star map. So what is the Zetianji star chart and what is its use? In the play, Chen Changsheng, under the guidance of Xun Mei, came to the location where Zhou Dufu observed the monument, and he saw the picture full of stars, which is the star map. This picture seems to be full of mystery and extremely profound. , Chen Changsheng put all his attention on the picture in order to reveal the secret and win a chance to change his life.