or descending) node of its orbit. The discovery of precession caused the <a href="https://en.wikipedia.org/wiki/Sidereal_year" target="_blank">sidereal year</a> as another cycle relevant to the superior epoch. At the superior epoch, the winter solstice point had to be located inside the <i>Emptiness mansion</i> (虛宿), which is in the present-day constellation Aquarius. The non-uniform motion of the Sun was discovered in the 6th century. However, it was assumed that the motion of the Sun was the fastest a