Astronomy and almanac

The xiu were used to fix the positions of the Sun, Moon and planets against the stars and to regulate the calendar, and in the almanac tradition each mansion governs a day and carries auspicious or inauspicious associations for particular acts, much as the Indian nakshatras and Arabic manazil do in their systems. The four palaces also organise the sky into the great animal constellations of Chinese cosmology.

The atlas gives each xiu its asterism, its palace and animal, and its associations. It is the Chinese member of the lunar-mansion family shared with the Indian nakshatras and Arabic manazil.