San Tai: one word, several uses

Where the book uses the words "San Tai"

In plain words first: the San Tai (三台) on a chart is a minor star counted from birth month and day, but the two characters mean more than that in the Zi Wei Dou Shu Quan Shu (紫微斗數全書), and they turn up in at least four kinds of places.

Open the full-size diagram

Layer sketch: each layer says which juan it comes from and what it refers to; only the first layer has a count by month and day, and its landings match iztro 2.6.0.

The first kind is the placement verse. Juan 2 has an entry on setting San Tai and Ba Zuo, where San Tai is a star to be put into some palace; the count comes in the next section.

The second kind is in the juan 1 entry for Zi Wei, and it is about three positions:

One must look at the three terraces: where Zi Wei guards the Life palace is the middle terrace, the place before it is the upper terrace, and the place after it is the lower terrace.

Here the "three terraces" are three seats in a row: the spot where Zi Wei holds the Life palace is the middle one, and the places before and after it are the upper and the lower. They follow where Zi Wei stands and are not counted from birth month and day.

The third kind is the verse lines about patterns, where the words stand beside ranks:

Ke bright and Lu hidden, a place among the three terraces; Sun and Moon in one palace, an office of marquis or earl.

"A place among the three terraces", the "marquis or earl" in the same line and the "rank of the three dukes" and "first rank" in the verses around it all speak of standing, and in old officialdom the three terraces often meant the highest grade of officials. Juan 3 adds a line "Zuo Fu (左辅) and Wen Chang (文昌), a place among the three terraces" used in the same way.

The fourth kind is two passages on "cleverness" and "military office", where San Tai and Ba Zuo are listed in one string with Zuo Fu, You Bi, Wen Chang and Wen Qu, and so are used as star names.

The book does not spell out how the four kinds relate, so what follows deals with the first one only.

Day 1 on the Zuo Fu palace, counted to the birth day

The rule itself is short: put the first lunar day on the palace where Zuo Fu sits, advance one palace per day in branch order, and the palace where the count stops at the birth day is San Tai. Juan 2 phrases it as taking "the first day and adding it to the Zuo Fu palace", then counting forward to the birth day.

Zuo Fu is set by birth month, at the Dragon palace for the first month and one palace further for each month, so the starting point of San Tai is fixed by the month; see Zuo Fu.

On day 1 itself San Tai shares the palace with Zuo Fu. Every twelve more days the landing comes back to the same place, so days 1, 13 and 25 put San Tai in one palace.

Month and day are one and the same in the formula

Put the two steps together: Zuo Fu is the Dragon palace plus (month minus one) places, and San Tai is Zuo Fu plus (day minus one) places, so San Tai is the Dragon palace plus (month plus day minus two) places. In the formula month and day sit in perfectly symmetric positions: one more month or one more day moves San Tai one palace on, so the landing depends only on the remainder of month plus day divided by 12.

Three different dates make a check:

The starting points differ and the step counts differ, yet the landing is one palace. The formula's results agree with charts drawn by the engine, and random spot checks turned up no exception.

Which day to count with

1. 1

   Fix the lunar month and day

   Apply the leap month and late-Rat-hour settings above to get the month and day used for the chart.

2. 2

   Add them and keep the remainder after 12

   Find the branch for that remainder in the table above.

3. 3

   Then use the Life palace for the name

   Once the branch is known, read which palace that branch is on this chart.

San Tai has a partner that counts the days in the opposite direction, covered in Ba Zuo; to read the palace it lands in, the order of the palaces is in the twelve palaces.