How to find constellations: a beginner's guide to the night sky

Before you start

• Find the darkest spot you can. A back garden away from street lights is fine; a park or the countryside is better.
• Pick a clear night, ideally near new Moon. A bright Moon washes out fainter stars, though the brightest patterns still show.
• Let your eyes adapt. It takes around 20 to 30 minutes for your night vision to build up, and one glance at a bright screen undoes much of it.
• Use red light. A red torch, or a red screen filter, lets you read a map without losing your dark adaptation.
• Dress warmly. Even summer nights get cold when you're standing still.

Measure the sky with your hand

Star maps give distances in degrees. Your hand, held at arm's length, makes a surprisingly good ruler, whatever your size:

Start here: the Plough and the North Star

If you're in the northern hemisphere (the UK, Europe, North America), the Plough, also called the Big Dipper, is the best first target. Its seven bright stars form a saucepan shape, and in the UK it never sets, so it's visible on any clear night of the year.

1. Find the Plough. Look north; it's high overhead in spring and low over the northern horizon in autumn.
2. Follow the pointers. The two stars at the end of the bowl point to Polaris, the North Star, about five times their own gap away. Polaris isn't especially bright, but it barely moves and always marks north.
3. Carry on past Polaris about the same distance again to reach the W shape of Cassiopeia.
4. Follow the curve of the handle ("arc to Arcturus") to the bright orange star Arcturus in Boötes.

Constellations through the year

Because the Earth goes round the Sun, different patterns are up in the evening at different times of year. A few landmarks for evenings in the northern hemisphere:

Is it a planet or a star?

A very bright "star" that isn't on your map is often a planet. Venus, Jupiter, Mars and Saturn are easy to see with the naked eye. Clues:

• Planets usually shine with a steadier light, while stars twinkle, especially low down.
• Planets stay near the ecliptic, the line the Sun and Moon follow across the sky.
• They move against the stars over days and weeks, which is why they're never printed on a fixed star chart.
• Venus is the brightest of all, low in the west after sunset or the east before dawn.

Finding constellations with Night Sky

Night Sky works out the sky for your place and time on your device, so you can check what you're looking at.

• Set your location with Use my location, or pick a listed city or enter coordinates, which also works offline.
• Point mode. On a phone, tap Point and hold it up to the sky. The map follows your phone's motion sensors. If the compass seems off, wave it in a figure-8.
• Tap anything, a star, planet or constellation, for details. Or hold your finger on the sky to name the brightest thing near it.
• Tonight shows which planets are well placed, the dark hours and upcoming meteor showers, such as the Perseids in August and the Geminids in December.
• Night mode turns the screen red to protect your night vision, and the moon button in the top bar switches it on.
• Time lets you scrub forwards and backwards by the minute, hour, day or month, so you can see what will be up later, and Born makes a poster of the sky on any date and place.

The live map, point mode, tonight's sky, time travel and standard posters are free, with no ads and no account. Night Sky Pro ($2.99 once) adds a guided tour, an eclipse finder and HD poster prints.

Common mistakes

• Expecting constellations to look like their names. Most are loose shapes; learn the bright stars first.
• Checking a bright phone screen every few minutes and losing your dark adaptation.
• Giving up after five minutes. The fainter stars appear as your eyes adjust.
• Looking for summer patterns in winter. Check what's actually up tonight.