How do I find constellations and planets in the night sky?

The sky is not memorised object by object. It is learned by fixing a few obvious patterns and then following lines and distances from them, which is why the same two or three signposts appear in every beginner's guide.

What you'll need

• A planisphere or a stargazing app
• A red-light torch
• Binoculars (optional)

Step by step

1. Find the Plough first.Seven bright stars, part of Ursa Major, visible all year from Britain. It is the anchor for the northern sky and the first pattern almost everyone learns.
2. Use the Plough to find Polaris.The two stars at the end of the 'pan' point upwards to Polaris, the north star, about five times the gap between them. Polaris marks true north and barely moves all night.
3. Follow the Plough's handle to Arcturus.Continue the curve of the handle — 'arc to Arcturus' — to a bright orange star, then continue on to Spica. Old mnemonics like this are how the sky is actually taught.
4. Find Orion in winter.Three stars in a short straight line form the belt, unmistakable from autumn to spring. It is the best signpost in the winter sky.
5. Use Orion's belt as a pointer.Down and left from the belt to Sirius, the brightest star in the sky. Up and right to orange Aldebaran and then the Pleiades cluster.
6. Learn the Summer Triangle.Vega, Deneb and Altair, three bright stars high overhead on summer evenings, spanning three constellations. It anchors the summer sky as Orion does the winter.
7. Tell a planet from a star.Planets shine with a steady light while stars twinkle, because planets show a tiny disc rather than a point. Planets are also always near the ecliptic, the line the Sun follows.
8. Know which planets are easy.Venus is brilliant, low in the west after sunset or east before dawn. Jupiter is very bright and shows four moons in binoculars. Mars is orange. Saturn is a steady yellowish point and shows rings in a telescope.
9. Understand how the sky moves.It turns roughly 15 degrees an hour through the night around Polaris, and the same star rises about four minutes earlier each night, so the seasonal sky shifts as the year goes on.
10. Measure with your hand.At arm's length, a little finger is roughly one degree, three middle fingers about five, a fist about ten and a spread hand about twenty. This makes chart distances usable in the field.
11. Use an app to confirm, not to look for.Work out where something should be from the chart, find it with your eyes, then confirm. Holding a phone up and following it teaches you nothing and destroys your night vision.
12. Look at the Moon properly.Around first or last quarter, not full. The line between light and dark is where shadows are longest and craters and mountains stand out most sharply.

Tips

• Two signposts — the Plough and Orion — get you to most of the naked-eye sky.
• Steady light means a planet; twinkling means a star.
• Use your hand at arm's length to measure degrees on the sky.

Common mistakes

• Trying to learn the whole sky at once — Eighty-eight constellations is overwhelming and most are faint and shapeless. Two or three signposts plus star-hopping covers far more sky and actually sticks.
• Navigating by holding a phone up to the sky — The bright screen destroys dark adaptation and you learn nothing, because the phone does the finding. Work out the position first, then look up.

If it doesn't work

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