Guides

How the night sky works and how to see more of it, explained clearly and with sources.

• How to find planets in the night skyFive planets are easy to see with the naked eye. Here is where to look, when, and how to recognise them.
• Moon phases explainedThe Moon is always half lit by the Sun. What changes is how much of that lit half we see from Earth.
• How to watch a meteor showerNo equipment needed: a dark sky, patience and the right hours after midnight.
• Lunar eclipses: what they are and how to watchEarth's shadow falls on the full Moon. It is safe to watch with your eyes, binoculars or a telescope.
• How to watch a solar eclipse safelyNever look at the Sun without a proper solar filter, except during totality. Here is how to watch safely.
• Twilight and dark sky: civil, nautical and astronomicalThe sky is fully dark only when the Sun is more than 18° below the horizon. Here is what happens before that.
• Magnitude: how star brightness is measuredLower numbers mean brighter, and five magnitudes are a factor of 100 in brightness.
• Altitude and azimuth: finding things in the skyTwo angles tell you exactly where to look: which direction, and how high.
• Opposition, conjunction and elongation explainedThree words from the planet calendar, and what they mean for when you can see each planet.
• Aurora and the Kp index: when can you see the northern lights?The higher the Kp index, the farther from the poles the aurora reaches. Dark, clear skies and a view to the north do the rest.
• How to see the International Space StationThe space station is a bright, steady point of light that crosses the sky in a few minutes. It is visible only when it is in sunlight while your sky is dark: within a few hours after sunset or before sunrise.
• How to observe a cometA comet rarely looks like the photos. In binoculars most comets are a soft, fuzzy patch with a hint of a tail. Only a bright one every few years shows a tail to the naked eye.
• How to learn the constellationsStart with one bright pattern you cannot miss, use it as a signpost to its neighbours, and come back a month later: the sky will have turned, and you will know a little more of it.
• Light pollution and dark skies: the Bortle scaleFrom a city centre you can count a few dozen stars. From a truly dark site you can count a few thousand, with the Milky Way bright enough to cast a shadow. The Bortle scale puts a number on the difference.
• Binoculars for stargazing: what to buy and what to look atA pair of 7x50 or 10x50 binoculars shows the craters of the Moon, the moons of Jupiter, dozens of star clusters and the Andromeda Galaxy, for a fraction of the cost of a telescope.