You don’t need a telescope to start knowing the sky — just a few clear evenings and the right first patterns. Begin with the Big Dipper, Orion or the Southern Cross, then work outwards. The table of all 88 below shows which ones you can see from your place tonight.
People in every culture have joined the brighter stars into figures — hunters, animals, canoes, rivers — to tell stories and to keep track of the seasons. Modern astronomy keeps the old Greek and Roman names, but a constellation today is an area of the sky rather than a stick figure, like a country on a map. In 1922 the International Astronomical Union settled on a list of 88, and in 1930 it published official boundaries drawn by the Belgian astronomer Eugène Delporte. Together they cover the whole sky without gaps, so every star, galaxy or passing comet lies in exactly one constellation.
Forty-eight of them go back to Ptolemy’s Almagest of about AD 150; one of those, the great ship Argo, was later split into Carina, Puppis and Vela. Twelve southern constellations, from the Toucan to the Bird of Paradise, come from Dutch navigators sailing to the East Indies in the 1590s. Johannes Hevelius added seven, among them the Lynx and the Lizard, in 1690, and Nicolas-Louis de Lacaille filled the gaps of the southern sky in the 1750s with fourteen more, many named after the instruments of his age — the Telescope, the Microscope, the Air Pump, the Pendulum Clock. A handful more, among them the Dove, the Unicorn and the Giraffe, came from mapmakers of the 16th and 17th centuries.
Asterisms are not constellations
Many of the most famous star patterns are asterisms: shapes that are part of a constellation, or that borrow stars from several. The Big Dipper (the Plough in Britain) is seven stars of Ursa Major. The Summer Triangle takes one bright star from each of Lyra, Cygnus and Aquila. One corner of the Great Square of Pegasus belongs to Andromeda, and the Teapot is the bright core of Sagittarius. Asterisms are often easier to find than the constellations they sit in, which makes them perfect stepping stones.
Nineteen of the best known, from the Summer Triangle to the Diamond Cross, have their own pages with a chart, how to find them and what is inside: see Star patterns, which also shows which of them are up tonight from your place.
The stars of a constellation are rarely related to one another. They simply lie in the same direction from us, at very different distances: the five stars of Cassiopeia’s W range from about 55 to more than 500 light-years away.
Why the constellations change
Through the night
The Earth turns once a day, so the stars rise in the east and set in the west, wheeling around a point in the sky called the celestial pole — 15° every hour. In the northern hemisphere Polaris marks that point almost exactly; in the southern hemisphere there is no bright star at the pole.
Through the year
As the Earth travels around the Sun, the night side faces a different direction in space. Each star rises about four minutes earlier every night — two hours a month — so the constellations on view at the same hour slowly change with the seasons. Orion fills winter evenings in the northern hemisphere (summer evenings in the southern), while Scorpius belongs to the northern summer. Constellations near the Sun’s position are simply lost in daylight for a few months.
With your latitude
The celestial pole stands as high above your horizon as your latitude. Stars closer to the pole than that never set: from London or Berlin, the Big Dipper and Cassiopeia are up all night, all year. An equally large cap around the opposite pole never rises at all. That is why the Southern Cross stays hidden from Europe and most of the United States, and why from Sydney the Big Dipper never properly clears the northern horizon. The table below lists, for each constellation, the latitudes from which you can see the whole of it.
Over thousands of years: precession
The Earth’s axis also wobbles like a spinning top, once in about 26,000 years — the slow motion that Hipparchus discovered. The celestial pole drifts among the stars as a result. When the pyramids were built the pole star was Thuban in Draco; today it is Polaris, which will come closest to the pole around the year 2100; in about 12,000 years Vega will be near it. Precession also explains why the Sun no longer stands in the zodiac constellations on the dates astrology gives them: the signs were fixed some 2,000 years ago, and today the Sun is roughly a month behind them — and it spends part of December in Ophiuchus, which no horoscope mentions.
How to start
Pick a clear, moonless evening, give your eyes twenty minutes to adapt, and learn one or two patterns per night. A sky map set to your place helps you match what you see; switch on the red night vision mode to keep your eyes dark-adapted.
In the northern hemisphere
Find the Big Dipper in the north — high on spring evenings, low over the northern horizon in autumn.
Follow the Pointers. Draw a line through the two stars at the end of the bowl, Merak and Dubhe, and continue about five times their separation to reach Polaris, the North Star. It is not especially bright, but everything else turns around it.
Cross to Cassiopeia, a W of five stars on the other side of Polaris, about as far away as the Dipper.
Then turn south. On winter evenings Orion stands in the south; on summer evenings look high up for the three bright stars of the Summer Triangle.
In the southern hemisphere
Find the Southern Cross in the southern half of the sky, with the two bright Pointers, Alpha and Beta Centauri, beside it.
Extend the long arm of the cross about four and a half times its length, in the direction its foot points. That brings you to the south celestial pole, an empty-looking patch of sky; σ Octantis, the nearest naked-eye star, is barely visible from a dark site.
Look north on summer evenings for Orion, which appears upside down, and overhead on winter evenings for the long curve of Scorpius.
Facing north: the Pointers of the Big Dipper lead to Polaris; Cassiopeia is on the other side. The whole pattern turns around Polaris once a day, so it may be tilted or upside down when you look.Facing south: extend the long axis of the Southern Cross about 4½ times beyond its foot to reach the south celestial pole. The Pointers show which cross is the real one.
Six constellations to know first
Evenings, December to March · seen from everywhere
Orion, the Hunter
Three stars in a short straight line — the Belt — make Orion the easiest constellation to recognise. Above and below it shine red Betelgeuse and blue-white Rigel. Hanging from the Belt is the Sword, and its middle “star” is a glow that even binoculars show: the Orion Nebula, a nursery of new stars about 1,300 light-years away. Follow the Belt one way to Sirius, the brightest star of the night, and the other way to orange Aldebaran and the Pleiades. From the southern hemisphere Orion appears upside down; many Australians call its Belt and Sword the Saucepan.
Seven bright stars of the Great Bear form the Big Dipper, an asterism called the Plough in Britain. The two stars at the end of the bowl are the Pointers to Polaris. In the bend of the handle, sharp eyes see two stars close together, Mizar and Alcor, and a small telescope splits Mizar itself in two. Follow the curve of the handle away from the bowl to orange Arcturus. Under a dark sky, extend the diagonal of the bowl from Phecda through Dubhe by about its own length and binoculars show two faint smudges: the galaxies M81 and M82.
Five stars in a W — or an M, depending on the hour — sit on the opposite side of Polaris from the Big Dipper, so when one is low the other is high. The W lies in the Milky Way, and sweeping it with binoculars shows a rich field of stars. Between Cassiopeia and Perseus, binoculars reveal the Double Cluster, two star clusters side by side. About 15° almost due south of Schedar, the brightest star of the W, lies the Andromeda Galaxy: a hazy oval on a dark night and, at 2.5 million light-years, the most distant thing easily seen with the naked eye. In 1572 Tycho Brahe’s “new star” blazed up here.
Three bright stars in three constellations make the Summer Triangle: Vega in Lyra, Deneb in Cygnus and Altair in Aquila. Cygnus, the Swan, flies down the Milky Way with Deneb at its tail; its main stars form the Northern Cross. At the Swan’s head is Albireo: a small telescope at 30× shows a golden star and a blue one side by side, one of the loveliest sights in the sky. Near Vega, the Ring Nebula is a tiny smoke ring in a small telescope, and about a third of the way from Vega to Arcturus the great globular cluster M13 in Hercules shows as a fuzzy star in binoculars.
One of the few constellations that really looks like its name: a curving line of stars ending in a raised sting. At its heart glows Antares, a red supergiant so large that, put in place of the Sun, it would reach beyond the orbit of Mars; its name means “rival of Mars”. Binoculars show the globular cluster M4 right beside Antares and, near the sting, two fine open clusters, M6 and M7, set against the Milky Way. From mid-northern latitudes Scorpius stays low in the south, and from northern Europe the sting barely clears the horizon, if at all; from the southern hemisphere it passes overhead on winter evenings.
The smallest of the 88 constellations, and one of the best known: it flies on the flags of Australia, New Zealand, Brazil, Papua New Guinea and Samoa. Four bright stars make a kite-shaped cross, with a fainter fifth star off-centre. Beside it, the two bright Pointers, Alpha and Beta Centauri, show which cross is the real one; a looser “False Cross” nearby fools many beginners. Alpha Centauri is the nearest star system to the Sun, 4.4 light-years away. Next to the cross lies the Coalsack, a dark cloud of dust against the Milky Way, and near Mimosa the Jewel Box cluster sparkles in binoculars and small telescopes.
Best evening is when the middle of the constellation is highest at about 9 pm local time (10 pm in summer time); a month earlier, the same view comes two hours later. It is the same date at every latitude. Whole of it from gives the latitudes from which every part of the constellation rises above the horizon at some time of year; part of it from, those where at least some of it does. Near those limits the edge only grazes the horizon, so allow ten degrees or so for a comfortable view. Names link to the sky map.
The 88 constellations: meaning, abbreviation, best evening month, the latitudes from which they can be seen, and area
Latitudes and dates are worked out from the official IAU boundaries (as implemented in Astronomy Engine) for the epoch J2000, ignoring refraction and hills on the horizon. Areas are the IAU values in square degrees, with the rank by size.