Zi Wei Dou Shu (Purple Star Astrology) (紫微斗數)

Zi Wei Dou Shu (紫微斗數, 'Numbers of the Purple Star of the Northern Dipper') is one of two principal systems of classical Chinese astrology alongside Ba Zi (#10). Its origin is traditionally attributed to the Daoist immortal Chen Tuan, who lived during the Five Dynasties era (10th century CE), although modern scholars point to a later systematization. Historically, the system was considered a court practice and was accessible only to the imperial court.

The foundation of the system consists of 12 palaces (宮, Gong) arranged in a square. Each palace governs a specific sphere of life: Life, Siblings, Spouse, Children, Wealth, Health, Travel, Servants, Career, Property, Karma, and Parents. Into each palace 'arrive' stars — principal and secondary — depending on the birth parameters. The main star — the Purple Star Zi Wei, the 'Polaris' of Chinese astrology — determines the type of destiny.

The system includes 14 major stars and approximately 100 minor ones; their configuration across 12 palaces creates a unique 'astral portrait' of the person. Interpretation requires knowledge not only of individual star meanings but also of their interactions, transformations (四化, si-hua), and 'flights' into other palaces. Decadal limits (大限, da-xian) — 10-year periods analogous to Da-yun in Ba Zi — are also factored in.

In the Errarium atlas, Zi Wei Dou Shu (#37) stands alongside Ba Zi (#10) and Qi Men Dun Jia (#38) as a Chinese metaphysical system. The key difference from Ba Zi: Ba Zi describes a person's nature through elemental balance, while ZWDS does so through an astral map of palaces and stars. ZWDS is considerably more detailed regarding specific life spheres and lends itself more readily to direct 'event-level' interpretation.