The autumn sky: the Great Square and Fomalhaut
Autumn has the fewest bright stars of any season, and the seven northern mansions of the Black Tortoise are mostly faint. But overhead there is an easy big square, the Great Square of Pegasus. In China it is the mansions Shi and Bi, anciently Yingshi, "the Encampment", a symbol of the palace. From it, go north to Cassiopeia and south to Fomalhaut.
The sky over Taipei, October 15, 9 p.m.
Taipei, October 15, 9 p.m.. The maps show the sky as you look up: north at the top, east on the left; the center is the zenith and the rim is the horizon. Planets and the Moon are left out because they move from year to year; use the tool on this page to see a given night.
You can see the same sky at about 7 p.m. in mid-November and about 11 p.m. in mid-September. The sky runs about two hours earlier each month, so the positions below work in other months if you shift the time.
All worked examples on these pages are calculated for Taipei (25°N). Further north, northern stars ride higher and southern ones lower; the tool on this page will redraw the sky for London, New York, Vancouver, Sydney and other cities.
Use this table to find them
| Target | Chinese name | Western name | Position, Oct 15, 9 p.m. | How to recognize it |
|---|---|---|---|---|
| Great Square: southwest corner | 室宿一 Shi Xiu Yi | Markab, Pegasus | southeast, about 79° up (nearly overhead) | Four similar stars near the zenith make a big square; the western two belong to the mansion Shi |
| Great Square: northeast corner | 壁宿二 Bi Xiu Er | Alpheratz, Andromeda | east, about 70° up | The eastern two belong to the mansion Bi; this one is actually in Andromeda |
| Cassiopeia | 王良四 Wang Liang Si | Schedar, Cassiopeia | northeast, about 52° up | Five stars in a W high in the north; in autumn use it instead of the Dipper to find Polaris |
| Polaris | 勾陳一 Gou Chen Yi (北極星) | Polaris, Ursa Minor | north, about 25° up | Extend a line out from the middle of the W; due north, about 25° up in Taipei |
| The southern first-magnitude star | 北落師門 Bei Luo Shi Men | Fomalhaut, Piscis Austrinus | south, about 35° up | A lone bright star low in the south with no other bright stars nearby, easy to spot |
| The Summer Triangle | 天津四 Tian Jin Si | Deneb, Cygnus | northwest, about 59° up | High in the west: Deneb, Vega and Altair, left over from summer |
Positions from our sky engine (Taipei, no refraction). Elsewhere in Taiwan the difference is small; further north, southern stars sit a few degrees lower for every degree of latitude you gain.
When the Dipper is gone, use Cassiopeia
At Taiwan's latitude the Big Dipper sinks to the northern horizon or below on autumn evenings (at 9 p.m. on October 15, Dubhe is about 3° below the horizon in Taipei). Use Cassiopeia on the other side of Polaris instead: five stars in a W (the Chinese asterisms Wangliang and Ce). Extend a line from the middle of the W about five times its width and you reach Polaris. Further north the Dipper stays above the horizon, low in the north, but Cassiopeia is still the easier guide in autumn.
The farthest thing you can see with the naked eye
From Alpheratz (Bi Xiu Er) at the Great Square's northeast corner, follow the chain of Andromeda's stars east two steps to Mirach (Kui Xiu Jiu, β Andromedae), then turn northwest past two faint stars. Beside them is an oval hazy smudge, the Andromeda Galaxy (M31), about 2.5 million light-years away and one of the most distant objects visible to the naked eye; it lies within the mansion Kui. You need a dark, moonless night.
Three common misconceptions
There is nothing worth seeing in autumn.
Bright stars are few, but the Great Square and Cassiopeia are easy to find, and autumn is a fine time to see the Andromeda Galaxy and the Pleiades rising.
All four stars of the Great Square belong to Pegasus.
The northeast corner, Alpheratz (Bi Xiu Er), belongs to Andromeda (α Andromedae); it is only borrowed to complete the square.
Fomalhaut is a northern star.
Fomalhaut is low in the south (in Piscis Austrinus). Its Chinese name, Beiluo Shimen, means the north gate of an army camp and has nothing to do with where it is in 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.
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.
Try another date: the sky on your night
Pick a date, time and place; the tool draws the whole sky with the Moon and planets marked.
The Autumn Sky FAQ
Where is the Great Square of Pegasus?
Near the zenith on autumn evenings: four stars of similar brightness making a big square. In the Chinese sky the western two are the mansion Shi and the eastern two the mansion Bi.
How do I find Polaris in autumn?
With the Dipper low, use Cassiopeia: five stars in a W. Extend a line from the middle of the W about five times its width to reach Polaris.
What star is Fomalhaut?
The brightest star in Piscis Austrinus, a lone first-magnitude star low in the south on autumn evenings. In the Chinese sky it stands for the north gate of an army camp.