Dou, the Dipper of the Black Tortoise

Dou, the Dipper, is the eighth of the twenty-eight xiu and the first mansion of the northern palace, the Black Tortoise, which holds the second group of seven and governs the direction north and the season of winter. This is the Southern Dipper, formed by stars in Sagittarius, distinct from the more famous Northern Dipper of the Great Bear. In the later astrological tradition its animal totem is the Unicorn. As one of the twenty-eight lunar mansions it tracks a segment of the Moon's monthly path. These are the conventions of the Chinese astronomical and calendrical tradition, in which the twenty-eight xiu order the sky into four palaces of seven mansions, the Black Tortoise, a tortoise entwined with a snake, spanning the northern quarter of the heavens.

Distinguishing this Southern Dipper from the far more famous Northern Dipper of the Great Bear, which anchors circumpolar navigation and Daoist ritual astronomy in a wholly separate part of the sky, is one of the more common points of confusion for readers new to the twenty-eight mansions; the Southern Dipper's seven stars in Sagittarius mark only the opening of the northern palace's own winter sequence and carry none of the pole-centred symbolism the Northern Dipper accumulated in later Chinese religious astronomy.