Chinese asterisms and Western constellations: finding them in the sky
Looking at the same night sky, Westerners see Orion, Scorpius and Cygnus; ancient Chinese astronomers saw the mansions Shen and Xin and the Celestial Ford. The two systems divide the sky differently and name it differently, yet they often point at the same stars. Learn how they line up and a handful of landmarks, and you can step outside and name much of the sky.
Tonight's sky: what is overhead right now
Pick a date, a time and a place to draw the whole sky at that moment, with the Moon, the planets, the bright stars that are up, and the Chinese lunar mansion crossing the meridian due south. Switch between Western constellation lines and Chinese asterisms. Everything is calculated in your browser.
Star catalog: about 1,600 Hipparcos stars brighter than magnitude 5 (compiled from d3-celestial, BSD license). The Moon and planets use simplified formulas accurate to within 0.3°; atmospheric refraction is ignored.
Two systems, two ways to divide the sky
| Western constellations | Chinese asterisms | |
|---|---|---|
| Current standard | The IAU fixed 88 constellations in 1922 and published their boundaries in 1930 | Chen Zhuo (3rd century) merged the catalogs of the Shi, Gan and Wu Xian schools; the usual count is 283 asterisms and 1,464 stars |
| How the sky is divided | Like a map of counties: the whole sky is cut into 88 areas and every star belongs to one | An asterism is a small pattern of stars (from one to dozens); together they do not cover the whole sky |
| Overall framework | By season, and by the twelve zodiac constellations | Three Enclosures around the north pole, plus 28 Mansions in a ring along the ecliptic and equator |
| Where the names come from | Mostly Greek myth, plus constellations added in the age of navigation | A heavenly court, market and officials mirroring society on earth |
| Main use | Labeling regions of the sky, observational astronomy | Tracking the Sun, Moon and planets, making calendars, omen reading |
In short, Western constellations are areas and Chinese asterisms are patterns. So one Western constellation often holds several asterisms: Orion contains the mansions Shen and Zi, and Scorpius contains Fang, Xin and Wei.
One star, two names
| Western name | Chinese name | Season | Why it is easy to spot |
|---|---|---|---|
| Sirius (Canis Major) | 天狼 Tian Lang, the Celestial Wolf | Winter | The brightest star in the night sky |
| Vega (Lyra) | 織女一 Zhi Nü Yi, the Weaving Girl | Summer | The brightest corner of the Summer Triangle |
| Altair (Aquila) | 河鼓二 He Gu Er, the Cowherd star | Summer | A small star on each side, like a carrying pole with two baskets |
| Antares (Scorpius) | 心宿二 Xin Xiu Er, "the Great Fire" | Summer | Very red, low in the sky |
| Orion's Belt | 參宿一、二、三 Shen Xiu 1–3 | Winter | Three equally bright stars in a straight line |
| The Big Dipper (Ursa Major) | 北斗 Bei Dou, the Northern Dipper | Highest in spring | Shaped like a ladle |
| Polaris (Ursa Minor) | 勾陳一 Gou Chen Yi | All year | Barely moves, always due north |
| The Pleiades (Taurus) | 昴宿 Mao Xiu, the Hairy Head | Winter | A tiny tight cluster of stars |
Learning the sky from scratch: three steps
1. Check whether "that bright one" is a planet
The first and brightest "star" to appear at dusk is often Venus or Jupiter. Planets shine with a steadier light, twinkle less, and drift against the stars over a few months, so star charts don't show them. The tool above marks where the planets are.
2. Start from a few big landmarks
The most useful landmark all year is the Big Dipper (for finding Polaris and the spring sky). In winter look for Orion, in summer the Summer Triangle and Scorpius, in autumn the Great Square of Pegasus. Find a landmark first, then "hop" from star to star.
3. Match the season and the hour
Earth's rotation turns the sky 15° westward every hour, and its orbit makes the same stars rise about two hours earlier each month. So "the winter sky" means the sky at 8 or 9 p.m. in winter; the same stars are visible in summer only before dawn. (Seasons here are Northern Hemisphere seasons.)
The skeleton of the Chinese sky: Three Enclosures and 28 Mansions
Chinese astronomers divided the region around the north celestial pole into three "enclosures", areas ringed by star walls: the Purple Forbidden Enclosure was the emperor of heaven's palace, the Supreme Palace Enclosure his court, and the Heavenly Market Enclosure a market (see the Three Enclosures). The band of sky that the Sun and Moon travel through was cut into twenty-eight segments, the 28 Lunar Mansions, grouped by direction into the Azure Dragon of the East, the Black Tortoise of the North, the White Tiger of the West and the Vermilion Bird of the South: the Four Symbols.
| 9 p.m. on the 15th (Taipei) | Mansion on the meridian (due south) | Symbol |
|---|---|---|
| January | 畢 Bi (Net) | White Tiger of the West |
| February | 井 Jing (Well) | Vermilion Bird of the South |
| March | 鬼 Gui (Ghost) | Vermilion Bird of the South |
| April | 張 Zhang (Extended Net) | Vermilion Bird of the South |
| May | 軫 Zhen (Chariot) | Vermilion Bird of the South |
| June | 亢 Kang (Neck) | Azure Dragon of the East |
| July | 心 Xin (Heart) | Azure Dragon of the East |
| August | 箕 Ji (Winnowing Basket) | Azure Dragon of the East |
| September | 牛 Niu (Ox) | Black Tortoise of the North |
| October | 危 Wei (Rooftop) | Black Tortoise of the North |
| November | 壁 Bi (Wall) | Black Tortoise of the North |
| December | 婁 Lou (Bond) | White Tiger of the West |
Calculated by our sky engine: the mansions are marked off by the right ascension of their determinative stars, and we check which one is due south in Taipei at 9 p.m. Local time matters more than latitude here, so the table holds well anywhere at 9 p.m. local time.
Three common misconceptions
The 28 mansions are 28 stars.
Each mansion is a group of stars, from two or three up to eight in Jing (the Well). One star in each is chosen as the "determinative star" from which the mansion is measured, which is where numbered names like Jiao Xiu Yi ("Horn 1", Spica) come from.
The Cowherd star is in the Ox mansion and the Weaver in the Girl mansion.
The Cowherd is Altair (He Gu Er, in Aquila) and the Weaver is Vega (Zhi Nü Yi, in Lyra), both far from the ecliptic. The Ox mansion (Niu) lies in Capricornus and the Girl mansion (Nü) in Aquarius, two very faint mansions.
In your birthday month you can see your zodiac constellation at night.
It is the other way round. Around your birthday the Sun is in that constellation, so it rises and sets with the Sun and is lost in daylight; it rides high at night about six months later. And because of precession, astrology's sign dates have slipped almost a whole sign away from the constellation the Sun is actually in; see the zodiac constellations.
Read on
A straight word: this is astronomy, not fortune-telling
These pages are about stars you can actually see: where they are, which season brings them, and what East and West call them. The "mansion of the day" in the Chinese almanac, the twelve signs of Western astrology and the stars of Zi Wei Dou Shu all borrow star names, but they are separate systems of calculation and do not match what is in the sky that night. Everything on this site is for reference and entertainment.
The Chinese calendar started with watching the sky
The Dipper's handle set the months and the Sun's position set the solar terms, and a BaZi chart's year, month, day and hour are built on that calendar. Enter your birth date to see your Four Pillars.
Chinese and Western constellations FAQ
How many constellations are there in the West, and how many Chinese asterisms?
The West uses the IAU's 88 constellations. The usual Chinese count is Chen Zhuo's 283 asterisms and 1,464 stars, of which the best known are the Three Enclosures and the 28 Lunar Mansions.
Do Chinese and Western constellations match one to one?
No. Western constellations divide the whole sky into 88 areas, while Chinese asterisms are small patterns of different sizes. Usually one Western constellation contains several asterisms; Scorpius, for example, holds the mansions Fang, Xin and Wei.
Can I see the constellations from a city?
Under city light pollution you can see stars down to about magnitude 2, enough to make out the Big Dipper, Orion and the Summer Triangle. For complete constellation figures you need to get out to the countryside or the mountains.
Which mansion is on the meridian tonight?
Use the "tonight's sky" tool on this page: pick a date, time and place and it draws the whole sky and tells you which mansion is due south.