《明史·志·卷十一》
求下一宫，逐次加上宫率三十度四三八一，满气象限减去，就得到各宫之下半交、中交后的宫界积度。
求次宫者，累加宫率二十度四三八一，满气象限去之，各得某宫下半产交后宫界积度。
To calculate the next palace, add the palace rate of 30 degrees and 4381 sequentially, subtract the full ecliptic, and obtain the accumulated intersection degrees of the palace boundary after half-intersection and mid-intersection under each palace.