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Every guide, path by path, 4 to 10 minutes each. Look one up by name, or keep only the ones good tonight from your sky.
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Soonest good night from your sky
Observing Skills 11 guides
Done — you can now go out on a night you planned, give your eyes the dark they need, and read the sky’s brightest stars.
- O1 Bright Stars of the Season Seen for real Which stars should you learn first, in a sky full of them? Five stars you can walk outside and find tonight — each one the door into its constellation.
- O2 Measure the Sky with Your Hand Seen for real How can your hand at arm’s length measure the sky? Your hand at arm’s length is a ruler for the sky — a finger, a fist, a spread hand — tried out on Orion, then used to find Sirius and to count a star’s height.
- O3 Understanding Star Brightness Seen for real Why does the brightest star in the night sky get a negative number? Why smaller numbers mean brighter stars — and how to read magnitudes off the sky with nothing but your eyes.
- O4 Dark Skies, Dark Eyes Seen for real Why do more stars appear the longer you stay outside? How dark your sky is, how dark your eyes are, and the half hour it takes your eyes to catch up — then averted vision for what is still too faint.
- O5 Binoculars First Seen for real Why is a pair of binoculars a better first instrument than a telescope? You do not need a telescope to start. What 10×50 means, why light beats magnification, and the Pleiades, the Orion Nebula, Jupiter's moons and the Moon's terminator in a pair.
- O6 Planning a Night Seen for real What should you check before you go out to look? Plan an observing night in the order you live it: the Moon and the clouds, then north, south and east, a first star-hop, the night as a graph, and what to pack.
- O7 Your First Telescope Seen for real Why does a telescope’s width matter more than its magnification? Aperture gathers the light and power only spreads it: the focal ratio and the field, the useful limit, the mount, and M13, Albireo, the Moon, Saturn and Jupiter in a small telescope.
- O8 Splitting Double Stars Seen for real How many stars is Mizar? From the pair the eye can split to the pairs that need a telescope and a steady night — and one whose stars have moved in your lifetime.
- O9 Stars That Keep Time Seen for real Which stars change brightness on a timetable? Algol dims as its companion passes in front; δ Cephei pulses and reddens — and the Cepheids measured the distance to the Andromeda Galaxy.
- O10 Light Pollution Seen for real Why does a city sky show so few stars, and how do you get them back? A city hides its stars behind its own glow, not its air: the same patch at Bortle 8 and Bortle 2, the limiting magnitude, and what you can do — shield lights, wait, go farther.
- O11 Phone Photos of the Night Seen for real Can the phone in your pocket photograph the stars? A phone held still gathers seconds of light: night mode on a tripod, the 500 rule for its lenses, the Milky Way and a conjunction, why zoom fails the Moon, and keeping your eyes dark.
How the Sky Turns 8 guides
Done — you can now say why the sky turns, and find your way round it from the pole stars.
- H1 Which Way Is East? Seen for real Why does the Sun rise due east only twice a year? The four points of your own horizon, a bearing round it and the point overhead — then where the Sun rises through the year, and why a star rises at the same point every night.
- H2 Finding the North Star Seen for real How can one star tell you how far north you are? Two stars in the Big Dipper's bowl point at Polaris, and Polaris tells you your latitude. That is the whole trick.
- H3 The Southern Cross Seen for real How do you find south from the stars, with no pole star to point the way? There is no south pole star. Crux and the two bright Centaurs are how you find the pole anyway.
- H4 Cassiopeia: The Other Pointer Seen for real How do you find Polaris when the Big Dipper is too low to use? When the Big Dipper is scraping the horizon, the W still finds Polaris — from the opposite side of the pole.
- H5 The Big Dipper & Friends Seen for real How can one star pattern lead you to four bright stars? One asterism, four departures: Arcturus, Spica, Polaris and Regulus, each on a line you can draw with your hand.
- H6 Four Minutes Earlier Seen for real Why does each star rise four minutes earlier every night? The Earth turns once against the stars a few minutes short of a day, so every star comes round four minutes earlier a night and two hours a month: why the evening sky changes with the seasons, and when your favourite comes back.
- H7 Why the Sky Moves Seen for real Why isn’t your sky tonight the same as someone else’s? Rotation, latitude and precession — the three reasons the sky you see tonight is not the sky someone else sees.
- H8 Celestial Coordinates Seen for real How do you give a star an address a telescope can find? Right Ascension and Declination: the two numbers that turn 'over there somewhere' into an address a telescope can drive to.
Sun and Calendar 9 guides
Done — you can now follow the Sun’s road through the year, and say what it does to your days and your calendar.
- Y1 Why We Have Seasons Seen for real Why are there seasons, if Earth is nearest the Sun in January? Earth is nearest the Sun in the northern winter. The seasons come from its tilted axis: how high your Sun climbs at noon, and how long it stays up.
- Y2 The Ecliptic Seen for real Why do the Sun, the Moon and the planets all keep to one track? One line across the sky carries the Sun, the Moon and every planet. Find it once and half of astronomy gets easier.
- Y3 The Sun's Year Seen for real Which stars is the Sun standing in front of tonight? Where the Sun is among the stars tonight, and the year-long walk along the ecliptic that makes the seasons.
- Y4 The Sun and Your Clock Seen for real Why does a sundial disagree with your clock on most days of the year? The earliest sunset comes before the shortest day and the latest sunrise after it. Why, and why a sundial is right four days a year at most.
- Y5 The Analemma Seen for real Why does the Sun, photographed at the same time each day, draw a figure-8? Photograph the Sun at the same time every day for a year and it draws a figure-8. What makes it tall, and what makes it wide and lopsided.
- Y6 Build an Analemma Seen for real What would the Sun’s figure-8 look like from Mars? Stand the Earth's axis upright, round off its orbit, move its perihelion, give it Mars's: watch the figure-8 change and see which cause makes which part.
- Y7 White Nights Seen for real Why do June nights in the far north never get properly dark? Why June nights in the far north never get properly dark, where the midnight Sun begins, and why Quito's nights hardly change all year.
- Y8 The Wandering Equinox Seen for real When does the Age of Aquarius actually begin? The point the whole sky is measured from is sliding out of Pisces. When it reaches Aquarius, and why the zodiac signs no longer match the stars.
- Y9 Ophiuchus, the Thirteenth Seen for real Which constellation on the Sun’s path do the horoscopes leave out? The Sun crosses thirteen constellations, not twelve — and spends longer in the Serpent-Bearer than in the Scorpion next door.
Constellations 5 guides
Done — you can now name the great figures of every season.
- C1 Orion: The Hunter Seen for real Where does Orion’s Belt point, in both directions? Seven bright stars, one straight line, and two of the sky's great landmarks at either end of it.
- C2 The Winter Hexagon Seen for real Which six bright stars make the grandest shape in the winter sky? Six first-magnitude stars from six constellations form the grandest pattern in the winter sky.
- C3 Leo & the Spring Sky Seen for real Which constellation actually looks like the animal it is named for? The one constellation that looks like its animal — and the signpost for everything else in the spring sky.
- C4 Scorpius & the Galactic Centre Seen for real Why does how far south you stand decide how high the Scorpion climbs? Follow the Scorpion's tail into the thickest part of the Milky Way — and learn why your latitude decides whether you get to.
- C5 The Summer Triangle Seen for real Which two lovers does the Milky Way keep apart? Three brilliant stars, three constellations, one love story written across the Milky Way.
Deep Sky 5 guides
Done — you can now find the clusters, nebulae and galaxies within reach of your eyes.
- D1 The Pleiades Seen for real How many of the Pleiades can you count with your own eyes? A thousand stars 444 light-years away, six of which you can see without moving from your doorstep.
- D2 The Orion Nebula Seen for real Where in Orion can you see stars being born? Hang a right off Orion's Belt into the nearest nursery of massive stars, where new ones are being made tonight.
- D3 Finding the Andromeda Galaxy Seen for real What is the farthest thing most people ever see with their own eyes? Star-hop from the Great Square to a trillion-star galaxy 2.56 million light-years away — the most distant thing most eyes ever see.
- D4 The Clouds of Magellan Seen for real What are the two clouds that never drift with the weather? Two pale patches by the south celestial pole that never move with the weather: the Large and Small Magellanic Clouds, galaxies beside our own.
- D5 The Plane of the Galaxy Seen for real Where is the centre of our galaxy in your sky? The Milky Way is our galaxy seen edge-on from inside. Find its midline, its centre in Sagittarius, and the empty window above it.
Moon 8 guides
Done — you can now say what the Moon will look like, how high it will ride, and when it will be eclipsed.
- M1 The Moon's Month Seen for real Why does a thin evening crescent grow into a full Moon? Why the Moon changes shape: a month of evenings, a crescent to a full Moon to a morning half, and the one angle that decides them all.
- M2 Not Earth's Shadow Seen for real Is the dark part of the Moon the Earth's shadow? The dark part of a crescent is not our shadow: the crescent sits beside the Sun while the shadow points away, a quarter's edge is straight, and the full Moon misses it. Only an eclipse shows the real one.
- M3 The Moon by Day, and Its One Face Seen for real Why is the Moon so often up in a blue afternoon sky? The Moon is not only a night thing: near a quarter, half its hours up are in a blue sky. And the one face it shows us means it turns once each trip round the Earth.
- M4 Supermoon Seasons Seen for real Why do supermoons nearly always come in threes? Why some full Moons come closer: two months that don't match, a 411.8-day beat, and supermoons that nearly always come in threes.
- M5 The Moon Illusion Seen for real Why does the rising Moon look so big? The rising full Moon looks huge, but ring it and it is no bigger: high up it is a hair wider, because you are nearer. The air only squashes it. The size is in the mind.
- M6 Eclipses Seen for real When is the next eclipse you can see from home? The Moon across the Sun and the Earth's shadow across the Moon: the next total, annular and lunar eclipses, why they line up, and the next ones you can see from home.
- M7 Eclipse Seasons Seen for real The Moon passes the Sun every month, so why so rarely in front of it? Why there isn't an eclipse every month: the Moon's path, the two nodes where it crosses the Sun's, and the seasons they make. Drawn for tonight.
- M8 The Moon's 18.6-Year Swing Seen for real Why does the Moon swing five degrees past the Sun’s limits in some years? Why the Moon swings five degrees past the Sun's limits in some years and stops five short of them in others: its path's tilt turning round, once in 18.6 years.
Planets 6 guides
Done — you can now tell a planet from a star, name it, and say where it will be next month.
- P1 Spotting the Planets Seen for real How can you tell a planet from a star? Five wanderers, five tells, and the one line in the sky they never stray far from. Positions are computed for tonight.
- P2 Why Planets Loop Seen for real Why would a planet ever go backwards? Mars stops and runs backwards for weeks: the loop on the sky, the loop as a plot, and the view from outside the orbits that explains it.
- P3 Venus's Eight-Year Star Seen for real How does Venus draw a five-pointed star every eight years? The evening star, the morning star, and the five-pointed pattern its meetings with the Sun draw on the zodiac every eight years.
- P4 Mercury's Hide-and-Seek Seen for real Why is Mercury so hard to catch, and when is it easiest? Mercury never strays more than 28° from the Sun, and whether that is enough depends on the season: the angle the ecliptic makes with your twilight horizon.
- P5 Racing and Crawling Seen for real Why does Halley’s Comet race past the Sun and crawl far from it? Why Halley's Comet rounds the Sun at 55 km/s and crawls past Neptune's distance at under 1: the line from the Sun sweeps equal areas in equal times.
- P6 The Lagrange Points Seen for real Where can a spacecraft keep pace with the Earth around the Sun? The five places where a spacecraft can keep pace with the Earth around the Sun, seen from outside the orbit, and where each one sits in your sky.
Visitors 7 guides
Done — you can now be outside on the right night for a meteor shower, a comet, the ISS or the aurora.
- V1 Comets Seen for real Why does a comet’s tail point away from the Sun? What a comet is, why its tails point away from the Sun, and where the dust goes — on Hale–Bopp's best night and Halley's, seen from where you are.
- V2 Meteor Showers Seen for real Why will you see fewer meteors than the forecast promises? Why a shower's meteors all fly from one point, why the count is never the brochure's, and how to watch one — on the Geminids' peak night.
- V3 Shooting Stars Aren’t Stars Seen for real What is a shooting star, if it is not a star? Every star is still there after the streak: a meteor is the light of a grain of comet or asteroid dust burning up 80–120 km overhead — Halley's, on the Orionids' peak — and a few strays fall on any dark night.
- V4 Satellites and the ISS Seen for real What is the steady light gliding across the sky at dusk? Why satellites shine at dusk and dawn, lit by a Sun you can no longer see; how fast they cross, why they never blink like a plane, Starlink trains, and how to find a real pass.
- V5 Satellite Orbits Seen for real Why is the ISS round again in 90 minutes, while a TV dish never moves? The ISS's orbit, drawn to scale round the globe, with polar, GPS and geostationary orbits: why each takes as long as it does, and where the geostationary belt sits in your sky.
- V6 A Visitor from Another Star Seen for real How do we know 3I/ATLAS came from another star? 3I/ATLAS, the third object ever seen from beyond the Solar System: where it was found, its best night from where you are, and the speed that proves it is not the Sun's.
- V7 Aurora Seen for real Where do you go to see the northern lights, and when do they come south? The northern lights are a ring round the magnetic pole, not the Pole: overhead in Tromsø and Fairbanks, out of sight at the Pole, and brought south to Edinburgh and London by a rising Kp.
Sky Cultures 7 guides
Done — you can now read the same stars the way other peoples have read them.
- S1 Before the Greeks Seen for real Who gave us the zodiac and the 24-hour day? The zodiac is Babylonian, the 24-hour day is Egyptian, and both were worked out by people watching this part of the winter sky.
- S2 The Star That Brought the Flood Seen for real Why did one star’s return at dawn open the year in ancient Egypt? Why Sirius vanishes each spring and returns one August dawn, Egypt's old new year, and why the Pleiades' return opens the Māori one.
- S3 The Chinese Sky Seen for real Whose palace did Chinese astronomers see at the pole of the sky? A sky built as a mirror of the imperial state: the emperor's palace at the pole, his carriage that tells the seasons, the Azure Dragon, the Great Fire, and the lovers across the Silver River.
- S4 The Moon's Houses Seen for real How long does the Moon take to come back to the same star? India, China and Arabia each split the Moon's road into 27 or 28 stations — and each drew its own figure on the same V of stars in Taurus.
- S5 Polynesian Wayfinding Seen for real How do you cross 4,000 km of open ocean with no instruments? One voyage, Tahiti to Hawaiʻi, across 4,000 km of open Pacific with no instruments: a star overhead, a cross on the horizon, and a compass made of rising points.
- S6 Shapes in the Dark Seen for real Can a constellation be made of darkness instead of stars? In the Andes and in Australia the constellations are the dust clouds between the stars: a llama, a tinamou and an emu.
- S7 The Sisters and the Hunter Seen for real Could an old story record a star in Orion changing brightness? The Western Desert, Greece and Arnhem Land all tell a story about the Pleiades and Orion — and some of those stories noticed that the stars change.
A word you do not know — magnitude, asterism, globular cluster — is explained in the field guide, with a real example that opens the map on it.