What are the middle palaces in the sky constellation?

In ancient times, the sky constellation was divided into five parts: east, west, south, north and middle, which were called the five palaces. In the middle is the Palace, which includes three walls: the upper wall is too small, that is, the starry sky, Zhang Su, plain clothes and the sky area north of plain clothes. The purple placanticline, that is, around the North Pole, includes an ordinary sky area in the Yellow River valley area of China (latitude about 36 degrees). Xiayuan Stone Sky City Wall, namely the sky area north of Su Fang, Shinjuku, Su Wei, Jisu and Dousu.