TL;DR: Placing the 14 major stars is the second step, after the 12 palaces have been set up and the five element cục of the Mệnh palace has been determined. From the cục and the lunar date of birth, the Tử Vi palace is found; then, following the verses in the Tử Vi đẩu số toàn thư, the Tử Vi constellation (Tử Vi, Thiên Cơ, Thái Dương, Vũ Khúc, Thiên Đồng, Liêm Trinh) moves backward, while the Thiên Phủ constellation (Thiên Phủ, Thái Âm, Tham Lang, Cự Môn, Thiên Tướng, Thiên Lương, Thất Sát, Phá Quân) moves forward. This is a convention of the Tử Vi Đẩu Số school, not a scientific conclusion about a person's fate.
What is placing the 14 major stars, and at which step of the chart does it fall?
Placing the 14 major stars is the step of assigning the 14 principal stars (Tử Vi, Thiên Cơ, Thái Dương, Vũ Khúc, Thiên Đồng, Liêm Trinh, Thiên Phủ, Thái Âm, Tham Lang, Cự Môn, Thiên Tướng, Thiên Lương, Thất Sát, Phá Quân) to the 12 palaces of the chart, after the 12 palaces have been built and the ngũ hành cục has been determined. This step decides the skeleton of the chart, because later interpretation looks first at the major stars in each palace.
Tử Vi đẩu số toàn thư, volume 2, opens with the rule for placing the Mệnh palace and the Thân palace by birth month and birth hour, then takes the nạp âm of the can chi of the Mệnh palace as the cục, and only from the cục and the birth date does it place the star Tử Vi[1]. The cục step is mandatory, because the Tử Vi palace depends directly on the cục and the lunar birth date.
How is the ngũ hành cục determined?
The ngũ hành cục is the nạp âm element of the can chi of the Mệnh palace, and the cục number (2, 3, 4, 5, 6) corresponds to that element. A commonly used quick method: assign a number to the heavenly stem (Giáp and Ất 1, Bính and Đinh 2, Mậu and Kỷ 3, Canh and Tân 4, Nhâm and Quý 5), assign a number to the earthly branch (Tý, Sửu, Ngọ, Mùi 1; Dần, Mão, Thân, Dậu 2; Thìn, Tị, Tuất, Hợi 3), add the two numbers, subtract 5 if the sum is greater than 5, then consult the table: 1 Mộc, 2 Kim, 3 Thủy, 4 Hỏa, 5 Thổ.
For example: the can chi of the Mệnh palace is Nhâm Thìn. Nhâm is 5, Thìn is 3, the sum is 8, subtract 5 leaves 3, which corresponds to Thủy, so it is Thủy nhị cục. The cục tells both the element and the number used to divide the birth date in the next step.
Note: the ngũ hành cục here is the nạp âm of the can chi of the Mệnh palace, not the nạp âm of the birth year. This is an easy point to confuse when constructing a chart by hand.
How do you find the Tử Vi palace from the cục and the birth date?
Finding the Tử Vi palace means dividing the lunar birth date by the cục number, then using the quotient and the remainder to determine the earthly branch of the Tử Vi palace. The commonly used calculation, which is also the one Nhật Nguyệt's calculation core uses: take the birth date and divide it by the cục number; count the quotient in the order Dần 1, Mão 2, Thìn 3, Tị 4, Ngọ 5, Mùi 6, Thân 7, Dậu 8, Tuất 9, Hợi 10, Tý 11, Sửu 12; if the division is not exact, add the smallest number that makes it exact; if the added number is odd, move backward, if the added number is even, move forward.
Three examples:
- Thủy nhị cục, born on day 28: 28 divided by 2 gives 14, 14 is greater than 12 so subtract 12 leaves 2, corresponding to Mão, so Tử Vi is placed at Mão.
- Mộc tam cục, born on day 25: 25 is not divisible by 3, add 2 to make 27, divide by 3 gives 9, corresponding to Tuất; the added number 2 is even so move forward 2 palaces (not counting the Tuất palace), reaching Tý, so Tử Vi is placed at Tý.
- Hỏa lục cục, born on day 15: add 3 to make 18, divide by 6 gives 3, corresponding to Thìn; the added number 3 is odd so move backward 3 palaces (not counting Thìn), reaching Sửu, so Tử Vi is placed at Sửu.
Tử Vi đẩu số toàn thư, volume 2, does not record the division; it prints five diagrams, one per cục, showing which palace holds Tử Vi for each birth date, and gives the example that a person of Hỏa lục cục born on day 1 starts Tử Vi at the Dậu palace[1]. The table below gives the first five days of each cục, computed with the division above:
| Cục | Day 1 | Day 2 | Day 3 | Day 4 | Day 5 |
|---|---|---|---|---|---|
| Thủy nhị cục | Sửu | Dần | Dần | Mão | Mão |
| Mộc tam cục | Thìn | Sửu | Dần | Tị | Dần |
| Kim tứ cục | Hợi | Thìn | Sửu | Dần | Tý |
| Thổ ngũ cục | Ngọ | Hợi | Thìn | Sửu | Dần |
| Hỏa lục cục | Dậu | Ngọ | Hợi | Thìn | Sửu |
How do the Tử Vi group moving counterclockwise and the Thiên Phủ group moving clockwise work?
Once the Tử Vi palace is known, place the 6 stars of the Tử Vi group in the counterclockwise direction, then place the 8 stars of the Thiên Phủ group in the clockwise direction. Tử Vi đẩu số toàn thư, volume 2, records the verse for the Tử Vi group: 紫微天机逆行旁，隔一阳武天同当，又隔二位廉贞地，空三复见紫微郎[1]. That is: after Tử Vi, move counterclockwise one palace to place Thiên Cơ, skip one palace to place Thái Dương, move counterclockwise one more palace to place Vũ Khúc, move counterclockwise one more palace to place Thiên Đồng, skip two palaces to place Liêm Trinh, skip three palaces and you meet Tử Vi again.
For the Thiên Phủ group, the Thiên Phủ palace must be found first. The book's diagram for placing Thiên Phủ states: only at Dần and Thân do Tử Vi and Thiên Phủ share a palace; at the other palaces the two stars mirror each other across the Dần Thân axis, for example Tử Vi at Sửu puts Thiên Phủ at Mão[1]. Once Thiên Phủ is known, the verse for the Thiên Phủ group is 天府太阴与贪狼，巨门天相及天梁，七杀空三破军位，八星顺数细推详[1], that is: Thiên Phủ, Thái Âm, Tham Lang, Cự Môn, Thiên Tướng, Thiên Lương, Thất Sát, then skip three palaces and at the fourth palace place Phá Quân.
The table below summarizes the relative positions of the 14 major stars by Tử Vi palace, based on the two verses above:
| Star | Group | Position | When Tử Vi is at Ngọ |
|---|---|---|---|
| Tử Vi | Tử Vi group | head of the group | Ngọ |
| Thiên Cơ | Tử Vi group | 1 palace counterclockwise from Tử Vi | Tị |
| Thái Dương | Tử Vi group | 3 palaces counterclockwise from Tử Vi | Mão |
| Vũ Khúc | Tử Vi group | 4 palaces counterclockwise from Tử Vi | Dần |
| Thiên Đồng | Tử Vi group | 5 palaces counterclockwise from Tử Vi | Sửu |
| Liêm Trinh | Tử Vi group | 8 palaces counterclockwise from Tử Vi | Tuất |
| Thiên Phủ | Thiên Phủ group | head of the group | Tuất |
| Thái Âm | Thiên Phủ group | 1 palace clockwise from Thiên Phủ | Hợi |
| Tham Lang | Thiên Phủ group | 2 palaces clockwise from Thiên Phủ | Tý |
| Cự Môn | Thiên Phủ group | 3 palaces clockwise from Thiên Phủ | Sửu |
| Thiên Tướng | Thiên Phủ group | 4 palaces clockwise from Thiên Phủ | Dần |
| Thiên Lương | Thiên Phủ group | 5 palaces clockwise from Thiên Phủ | Mão |
| Thất Sát | Thiên Phủ group | 6 palaces clockwise from Thiên Phủ | Thìn |
| Phá Quân | Thiên Phủ group | 10 palaces clockwise from Thiên Phủ | Thân |
A way to remember: the five later stars of the Tử Vi group sit 1, 3, 4, 5 and 8 palaces counterclockwise from Tử Vi; the seven later stars of the Thiên Phủ group sit 1, 2, 3, 4, 5, 6 and 10 palaces clockwise from Thiên Phủ, with three empty palaces between Thất Sát and Phá Quân. The example in the last column changes with the Tử Vi palace: the absolute position of each star changes with the Tử Vi palace, but the relative order among the stars within the same group is fixed. The chart maker only needs to remember the two verses to place all 14 major stars.
Why does the Tử Vi group move counterclockwise while the Thiên Phủ group moves clockwise?
Tử Vi đẩu số toàn thư gives no reason. The verse only records the direction: the Tử Vi group 逆行 (moves counterclockwise), the Thiên Phủ group 八星顺数 (eight stars counted clockwise)[1].
Because the two groups run in opposite directions, a palace may hold two major stars, one major star, or none (a palace with no major star, vô chính diệu). This is a technical convention of the discipline, not an astronomical phenomenon verifiable by observing the sky.
Do all books place them the same way?
At this step, yes. The verses for the two groups, the diagram for placing Thiên Phủ and the five diagrams for starting Tử Vi by cục in Tử Vi đẩu số toàn thư, volume 2[1], are the method for the 14 major stars that Nhật Nguyệt's calculation core uses; dividing the birth date by the cục number is simply a way to compute the same result.
The book names the cục 水二局, 木三局, 金四局, 土五局, 火六局[1], read in Sino-Vietnamese as Thủy nhị cục, Mộc tam cục, Kim tứ cục, Thổ ngũ cục, Hỏa lục cục.
Is placing the 14 major stars a prediction of destiny?
No. Placing the 14 major stars is only the step of assigning star positions according to the convention of Tử Vi Đẩu Số. The act of placing stars itself says nothing about the character or destiny of the person whose chart it is. The interpretation that follows is the interpretive part, and every interpretation belongs to the domain of the discipline's beliefs, not to scientific conclusions.
Nhật Nguyệt's suggestions for placing the 14 major stars yourself
Nhật Nguyệt's suggestion: if you construct a chart by hand, follow the order of four steps. One, determine the lunar birth date and birth hour. Two, place the 12 palaces and determine the Mệnh palace. Three, calculate the ngũ hành cục from the can chi of the Mệnh palace. Four, look up the Tử Vi palace and place the two groups in the correct direction. When consulting tables, cross-check at least two sources because some printed tables may contain errors. If the results differ, recheck the cục calculation first, because a wrong cục will lead to all 14 major stars being wrong.
Frequently asked questions
Is the lunar or the solar birth date used to place Tử Vi?
The lunar birth date is used. The method divides the lunar birth date by the cục number, counting the quotient in the order Dần 1 to Sửu 12. If you only have the solar date, convert it to the lunar date before placing stars.
What if the division is not exact?
Add the smallest number that makes it exact. If the added number is odd, move backward; if the added number is even, move forward, not counting the original palace. For example, Mộc tam cục on day 25, add 2 (even) so move forward 2 palaces from Tuất to Tý.
Can the 14 major stars be placed without knowing the cục?
No. The cục is the condition for looking up the Tử Vi palace. The method divides the birth date by the cục number. Without the cục there is no quotient, the Tử Vi palace cannot be determined, and therefore the 14 major stars cannot be placed.
