Most of the fourteen main stars are named for what they do. 太阴 (tài yīn) is named for what it is — the Moon — and most English introductions stop there, filing it under "gentle, intuitive, nurturing". The classical text is more specific, and far more useful. 《紫微斗數全書》 卷一·諸星問答論 opens its entry — 問太陰星所主若何 — with a job title rather than a temperament: 太陰乃水之精，為田宅主，化富 — "the essence of water, lord of the Property palace, transforming into wealth."
That line changes the reading. 太阴 is not mainly a soft personality; it is the part of a chart that describes what accumulates — savings, property, reserves, memory, the things that build up quietly and are never staged for an audience.
What the star means is computed, not guessed: the seat is arithmetic, the grade is a lookup, and both reproduce from the same birth data every time.
| Question | Answer |
|---|---|
| What is 太阴? | The Moon Star — water, accumulation, the Property palace, what is stored rather than shown |
| Where does it sit? | One step forward of 天府, the Treasury Star |
| Strongest seats | 亥, 子, 丑 in 廟 |
| Weakest seats | 卯, 辰, 巳 in 陷; 午, 未 in 不得地 |
| Does a low grade mean bad luck? | No — it grades how much light reaches that seat, not how good the life is |
| Which stars can share its palace? | 天机, 太阳, 天同 — or it stands alone |
太阴 belongs to the 天府 series — eight stars hanging off 天府, itself a mirror image of 紫微: it sits as many boxes back from 紫微 as 紫微 has advanced from 寅, computed as (12 − 紫微) mod 12. 太阴 takes the box right after 天府.
| Star | Series | Offset from 天府 |
|---|---|---|
| 天府 Treasury | 天府 | 0 |
| 太阴 Moon | 天府 | +1 |
| 贪狼 Greedy Wolf | 天府 | +2 |
| 巨门 Gate | 天府 | +3 |
| 天相 Minister | 天府 | +4 |
| 天梁 Elder | 天府 | +5 |
| 七杀 Seven Killings | 天府 | +6 |
| 破军 Destroyer | 天府 | −2 (+10) |
Two consequences follow, both checkable in any chart. The Moon can never sit more than one box from 天府, which is why the classical reading pairs it with the treasury and talks about accumulation rather than expression. And when 紫微 sits on the mirror axis at 寅, 天府 lands there too, pushing the Moon to 卯 — the seat the book grades 陷.
Twelve Emperor seats, twelve Moon seats. The grade column is the classical brightness rating (廟 旺 得地 利 不得地 陷), not a judgement.
| 紫微 at | 太阴 at | Grade | Reading |
|---|---|---|---|
| 寅 | 卯 | 陷 | The moon before dawn: the work is done in the dark and the credit arrives later |
| 卯 | 寅 | 旺 | A setting moon with a long tail — small gains that keep paying |
| 辰 | 丑 | 廟 | The moon high in the night sky; the storage seats, where assets hold |
| 巳 | 子 | 廟 | Peak of the night: the seat the book's wealth line describes |
| 午 | 亥 | 廟 | The moon at its own gate — 得垣, the top of the scale |
| 未 | 戌 | 旺 | A settled, bright moon: steady accumulation, little drama |
| 申 | 酉 | 旺 | Evening moon — good for craft, property and long games |
| 酉 | 申 | 利 | Workable light: competence that shows up in stages |
| 戌 | 未 | 不得地 | Light behind cloud: the accumulation happens, the recognition lags |
| 亥 | 午 | 不得地 | The moon at noon — capacity with no natural audience |
| 子 | 巳 | 陷 | Light lost before dawn; effort early, return late |
| 丑 | 辰 | 陷 | Overcast: the lowest of the twelve for this star |
This is the rare place where a classical sentence and a computed table can be compared line by line. In 卷一·諸星問答論, the commentary attributed to 希夷先生 divides the twelve seats in one clause:
以卯辰巳午未為陷地，以酉戌亥子丑為得垣。
卯, 辰, 巳, 午 and 未 are the 陷 seats; 酉, 戌, 亥, 子 and 丑 are the well-placed ones.
Five seats on one side, seven on the other — exactly the split in the table above, including the two 不得地 grades at 午 and 未. Nothing in the text needed softening to match.
The same chapter's wealth line covers the top of the scale: 太陰入廟有光輝，財入財鄉分外奇 (卷一·女命骨髓賦, 論定人富足) — at 廟 the Moon has light, and money in the money palace reads as exceptional there. That is a statement about which seat is under discussion, not a promise.
Take lunar 1990, fourth month, fifteenth day, 22:00 — a 庚 year. The engine places 紫微 at 午 (廟), which fixes everything downstream.
| Step | Result |
|---|---|
| 紫微 | 午 — 廟 |
| 天府 (mirror of 紫微) | 戌 — 得地 |
| 太阴 (+1 from 天府) | 亥 — 廟, the top of the Moon's scale |
| 太阳 (−3 from 紫微) | 卯 — 廟, the top of the Sun's scale |
| 天机 (−1 from 紫微) | 巳 — 平和 |
There was never another option: 紫微 at 午 forces 天府 to 戌, and 天府 at 戌 forces the Moon to 亥. The 庚 stem then attaches 化祿 to 太阳, 化權 to 武曲, 化科 to 太阴 and 化忌 to 天同 — so this chart's Moon carries 化科. The same 太阴 at 亥 under a different stem would carry nothing.
| Stem | What it attaches to 太阴 |
|---|---|
| 乙 | 化忌 (Ji) |
| 丁 | 化祿 (Lu) |
| 戊 | 化權 (Quan) |
| 庚 | 化科 (Ke) |
| 癸 | 化科 (Ke) |
Two things stand out. Only one stem gives the Moon 化祿 and only one gives it 化權 — narrow, next to 太阳 or 武曲, which several stems reach. And 太阴 is the only main star that receives 化科 from two different stems. The full 40-value table is in our guide to the four transformations.
| Strengths | Blind spots |
|---|---|
| Accumulates without needing applause | Under-claims, then feels invisible |
| Reads a room before speaking in it | Acts on the reading instead of asking |
| Keeps reserves — money, time, goodwill | Holds on past the point where holding costs |
| Remembers what people said they needed | Remembers slights longer than anyone else does |
| Steady in a crisis; others calm down around them | Absorbs the tension and shows the bill later |
One mechanism, two sides: the reserve-building behind the left column is the behaviour behind the right one; the star does not separate them.
Three errors account for most bad 太阴 readings.
Reading it as a personality type. The star is a flow direction: what comes in and stays, versus what goes out and is seen. A chart can be full of 太阴 and still describe someone forceful — the Moon says where the reserves are, not how loud the person is.
Treating a low grade as bad luck. The scale is taken literally: the Moon is graded by whether it is up. 陷 means the light is not available in that setting — read as lateness and indirection, not deficiency. 午, the Moon at noon, is the clearest case: capable, and structurally unobserved.
Reading 太阴 as "a female star" and then reading the person. The designation is relational: 男為妻宿，又作母星 — in a man's chart it marks the spouse star and the mother star. That is about which relationships the star indexes, not a claim about character or gender.
The character stays put; the palace names the arena where accumulation happens.
| Palace | What the placement emphasises |
|---|---|
| Life 命宮 | A private, self-contained style: reserves held out of view |
| Wealth 財帛 | Savings, property, income that compounds quietly |
| Career 官祿 | Behind-the-scenes work: research, design, care, back-office depth |
| Property 田宅 | The star's home palace — long-held assets and a home that is a base |
| Health 疾厄 | Where stored tension surfaces: sleep, eyes, fluid balance |
Only four arrangements are geometrically possible for this star.
| Configuration | Where it happens | What it settles into |
|---|---|---|
| 太阴 + 天机 | 寅, 申 | Planning joined to reserves: analysis that is stored and reused |
| 太阴 + 太阳 | 丑, 未 | 日月同宮 — the public and the private in one room |
| 太阴 + 天同 | 子, 午 | Ease plus accumulation: comfort that is quietly funded |
| 太阴 alone | 卯, 辰, 巳, 戌, 酉, 亥 | The purest form — accumulation with no filter or cover |
Two conditions change the reading rather than the position. 日月反背 is the case where the Moon sits at 卯 and the Sun at 亥 (紫微 at 寅) — both graded 陷; 卷一·斗數骨髓賦 notes 日月最嫌反背乃為失輝, a statement about light, not about capacity. And the same entry prefers the Moon without 巨门 beside it: 若上弦下弦，仍以不逢巨門為佳 — a reminder that the Gate star's scrutiny is the one thing the Moon is said to gain nothing from.
Run the same data next month and the Moon lands in the same box with the same grade; only the wording moves.
Try it free: enter your birth details at askziwei.com, find your Moon, and check its seat, its grade and whether a stem is attached to it this year. Then come back tomorrow and watch the conclusion hold.
What does the 太阴 star mean in Zi Wei Dou Shu? 太阴 (Tai Yin), the Moon Star, is the main star of the Property palace — the part of a chart that describes what accumulates rather than what is displayed. The classical entry names it before it describes it: water essence, lord of the Property palace, transforming into wealth.
Is a bright 太阴 better than a weak one? Not in the way people expect. The grade says how much of the star's light reaches a seat, and the Moon's scale is a night scale: strongest at 亥, 子, 丑, weakest at 卯, 辰, 巳. A low grade means accumulation that is indirect or late, not an unlucky chart.
Why is 太阴 paired with 天府? Because it sits in the 天府 series: 天府 is the mirror point of 紫微 across the 寅–申 axis, and the Moon takes the box right after it. Its seat is derived from 紫微's, never assigned on its own.
What is 日月反背? The Moon at 卯 with the Sun at 亥, both graded 陷 — it happens when 紫微 sits at 寅. The classical note, 日月最嫌反背乃為失輝, reads as a statement about available light rather than about ability.
Which year stems attach a transformation to 太阴? 丁 gives 化祿, 戊 gives 化權, 乙 gives 化忌, and 庚 and 癸 both give 化科 — the only main star to receive 化科 from more than one stem.
Curious where the Moon Star sits in your chart?
✦ Generate Your Chart — It's Free