The first system of astrology in China was known as “Five-Star System – Wu Xing Shu 五星術”. It uses the five planets:
Jupiter 【歳星】 – Wood Star
Mars 【荧惑】 – Fire Star
Saturn 【鎮星】 – Earth Star
Venus 【太白】 – Gold Star
Mercury 【辰星】 – Water Star
Later, the Sun 【Tai Yang 太陽】 and the Moon 【Tai Yin 太陰】 were included.
These were real heavenly bodies and astronomical calculations were used to locate them for astrological purposes.
There were four other heavenly bodies introduced:
【紫氣】 – Wood Residue
【月孛】 – Water Residue
【羅睺】 – Fire Residue
【計都】 – Earth Residue
The system is now known as Seven Proper and Four Residues (七政四餘).
The four residues are speculatively associated with Neptune, Uranus, Pluto and a Comet.
Both Zi Ping Shu (子平術) and Zi Wei Dou Shu (紫微斗數) were inventions to replace Qi Zheng Si Yu. They both gave up using real astronomy to do the charting. Zi Ping Shu or Four Pillars Destiny Analysis (四柱命理學) uses the ten stems and twelve branches but some special combinations owe their origin to Qi Zheng Si Yu. For example, stars used in Zi Ping Shu like Hong Luan 红鸞, Tian Yi Gui Ren 天乙貴人 have the corresponding stars in Qi Zhen Si Yu. Likewise, they also appear in Zi Wei Dou Shu.
The stars we use in Zi Wei Dou Shu have a lot in common with the real stars in Qi Zheng Si Yu. However, it is interesting to note that the names of some major stars are based on names derived from Buddhism. For example:
The Chinese names of the stars in the Big Dipper are:
(1)Tian Shu 天樞 (2) Tian Xuan 天璇 (3) Tian Ji 天璣 (4) Tian Quan 天權 (5) Yu Heng 玉衡 (6) Kai Yang 開陽 (7) Yao Guang 摇光
The corresponding names used in Zi Wei Dou Shu are:
(1)Tan Lang 貪狼 (2) Ju Men 巨門 (3) Lu Cun 祿存 (4) Wen Qu 文曲 (5) Lian Zhen 廉貞 (6) Wu Qu 武曲 (7) Po Jun 破軍
Suffice it to say that the stars we use in Zi Wei Dou Shu are virtual stars pretending to be the real stars we see on the sky. In other words, it is a system of life reading but only virtual astrology.