How do I look at the Moon properly?

The Moon is the one astronomical target that is genuinely impressive in any instrument, is unaffected by light pollution, and is available from a city centre garden. It is also the object most often looked at on the wrong night. Understanding the terminator changes the whole experience.

What you'll need

• Binoculars or any telescope
• A Moon map or app
• A red torch
• Something to lean on or a tripod

Step by step

1. Choose the phase, not the night.First quarter — the half Moon in the evening sky, about a week after new — is the classic time, high in the evening and beautifully lit. Last quarter is the same in the pre-dawn sky. Anything from a thin crescent to a fat gibbous is good. Full Moon is the exception, not the target.
2. Understand the terminator.The line dividing lunar day from night is where the Sun sits low on the lunar horizon. There, crater walls and mountains cast shadows across the surface and the relief leaps out in three dimensions. Watch the same crater on successive nights and the shadows change dramatically as the lunar sun rises.
3. Know why full Moon is flat.At full Moon the Sun is directly behind you, so there are no shadows at all. The surface looks bright, washed out and two-dimensional. It is also dazzling — enough to spoil your night vision for half an hour and, in a telescope, genuinely uncomfortable.
4. Start with the naked eye.The dark patches are the maria, ancient lava plains, and they have names worth knowing — Mare Tranquillitatis, Mare Imbrium, Oceanus Procellarum. The bright rays radiating from Tycho near the southern limb are visible without any optics at full Moon.
5. Use binoculars next.Any binoculars show the maria clearly, the larger craters along the terminator, and the mountain ranges. Brace them against a wall or a doorframe, or mount them on a tripod — the difference between hand-held and supported is enormous.
6. Work along the terminator with a telescope.Follow the line from one end to the other at moderate magnification. Copernicus, Tycho, Plato, the Apennine mountains, the Straight Wall, the crater chains and the flooded ghost craters all appear as the light angle suits them. There is more detail than any single night can cover.
7. Use a Moon map or app.Naming features turns a beautiful blur into a landscape you know. A simple Moon map, a phone app or a laminated card is enough, and features become old friends within a few sessions.
8. Deal with the brightness.Near full Moon, a telescope gives an uncomfortably bright image. A variable polarising filter, a neutral density Moon filter, or simply observing when the Moon is not full all work. Stopping the aperture down with a mask also works and costs nothing.
9. Look for earthshine on a crescent.On a thin crescent, the dark part of the disc glows faintly — sunlight reflected off the Earth onto the Moon and back. It is visible to the naked eye and lovely in binoculars, and it is best in spring evenings and autumn mornings.
10. Watch a lunar eclipse when one comes round.Total lunar eclipses are visible from the whole night side of the Earth, need no equipment and no filters, take a couple of hours, and turn the Moon a deep copper red. They are among the easiest and best astronomical events to see from Britain.
11. Photograph it with what you have.A phone held to a telescope eyepiece produces a surprisingly good Moon photograph, and a camera with a long lens on a tripod does better. The Moon is bright, so short exposures and low ISO work — treat it like a daylight subject, because that is what it is.

Tips

• Watching the same crater over three or four consecutive evenings is the exercise that makes the Moon a place rather than a picture.
• The Moon is high in winter and low in summer for the same phase, because it follows roughly the opposite path to the Sun. Winter first-quarter Moons are well placed.
• Libration — a slight rocking of the Moon over the month — lets you see slightly round each limb at different times, so the features at the edge change.
• A bright Moon washes out everything else in the sky. Plan deep-sky observing for the dark fortnight around new Moon and lunar observing for the rest.
• Occultations, where the Moon passes in front of a star or planet, are worth catching. Astronomy magazines and apps list them.

Common mistakes

• Waiting for the full Moon to look at it — It is the flattest, most glaring and least interesting phase. The quarters and crescents show the surface relief that makes it worth looking at.
• Using very high magnification — Atmospheric turbulence limits what any telescope can resolve on most British nights. Moderate power gives a sharper, more detailed view.
• Observing full Moon through a telescope with no filter and then trying to look at anything else — It destroys dark adaptation for half an hour or more, so plan the session with the Moon last.

Questions people ask