Tiān Jī

天機 stands one palace behind 紫微, counted against the order of the branches, and the placing verse names it in its very first line. Since that gap never varies, the position of 紫微 settles this star at once. In the table the calculator uses, its brightness runs in matched pairs of opposite palaces: temple at 子 and 午, prosperous at 卯 and 酉, gaining at 寅 and 申, benefiting at 辰 and 戌, neutral at 巳 and 亥, fallen at 丑 and 未.

The book assigns it to wood and calls it the third star of the Southern Dipper, a good star that adds to a person's count of years. Its name for the star's transformed energy is simply 善, goodness. The first answer in 卷一 links it to adaptability, respect for relatives, and quiet places and monastic life, and 卷二 names it the lord of the Siblings palace. The 卷二 entry says that in a temple position the temperament is quick and the heart kind, with plans that change often.

Three stars can share its palace: 太陰 at 寅 and 申, 巨門 at 卯 and 酉, 天梁 at 辰 and 戌. The text is specific about the last pairing: the two together are good at talking strategy. One line in 卷一 has it good among the good and harsh among the harsh, and the passage credited to 玉蟾先生 says that even under clashing stars it leans toward good. It is one of three main stars that can take each of the four transformations, with 乙 giving 化祿, 丙 化權, 丁 化科 and 戊 化忌.