Phase 7 of 8 Next: Saturday 3 October 2026

The Last Quarter

Half lit again, and shrinking — the opposite half from first quarter, lit from the other side.

Where to look: Rises around midnight, is highest at sunrise, and sets around noon. This is the quarter almost nobody sees, for scheduling reasons rather than astronomical ones.

The terminator is back in the middle and the shadows are long again, so the craters are as good as at first quarter — better, if anything, because the pre-dawn air is usually steadier than the evening air. The catch is that you have to be up at four in the morning to find out.

Commonly muddled: Also called third quarter. Same phase, same moment, two names, both in current use.

#003Phases & orbitThe Moon rises about 50 minutes later each night, which is why a waning Moon feels like it's avoiding you.In one day the Moon moves roughly 13° eastward along its orbit, and Earth needs about 50 extra minutes of spin to…U.S. Naval Observatory

#009ObservingPoint binoculars at the line between light and dark. That's where the Moon stops being a disc and becomes a landscape.Along the terminator the Sun sits near the lunar horizon, so crater rims cast long shadows and mountain peaks catch…NASA Moon observing

#071Phases & orbitNobody in an observatory calls it a half moon. "First quarter" counts the orbit, not the shape.By the time half the disc is lit, the Moon has covered 90° of its circuit, one quarter of the way from new moon to…U.S. Naval Observatory

#072Strange but trueAround 270 BC, a Greek worked out how far away the Sun is using nothing but a half moon and an angle.When the Moon is exactly half lit, the Sun, Moon and Earth form a right angle at the Moon, so measuring the…Aristarchus, On the Sizes and Distances (c…

#074GeologyThere is a 110-kilometre cliff on the Moon that looks drawn with a ruler. It's a black line after first quarter and a white one after last.Rupes Recta, the Straight Wall, is a fault where the crust dropped a couple of hundred metres along an almost…Lunar Reconnaissance Orbiter

#076ObservingThe line between light and dark on a waxing moon is a sunrise. On a waning moon it's a sunset. You are watching dawn cross another world at cycling pace.The terminator sweeps the lunar equator at about 15 km/h. On the waxing half it is the morning line, uncovering…NASA Moon observing

#077ObservingSerious lunar observers look at the same crater twice a month, because at last quarter the shadows fall the other way.The Sun rises over a feature during the waxing half of the cycle and sets over it during the waning half, lighting…Lunar and Planetary Institute

#078ObservingMajor observatories schedule their whole year around the Moon. The nights near new moon are called dark time, and astronomers fight over them.Telescope committees split the calendar into bright, grey and dark time by lunar phase. Faint galaxies and distant…Observatory time-allocation practice (ESO…

#086ObservingMost people who notice the Moon in daylight are looking at a waning one, through a windscreen, on the way to work.After full moon the Moon rises later each night and is still well up after sunrise, so the waning gibbous and last…U.S. Naval Observatory

#089ObservingThe fortnight after full moon is when the sky quietly comes back. Every night the Moon arrives later, and every night you can see more.From full to new, moonrise slides from sunset all the way round to sunrise, handing the early evening back to…NASA Moon observing

#151ObservingThe line between lunar day and night creeps along the Moon's equator at about 15 kilometres an hour, and much slower nearer the poles.It follows from a 10,900-kilometre circumference and a 29.5-day day. At the equator you would need a bicycle to…NASA Moon facts

#156ObservingThe length of a shadow, the height of the Sun above the lunar horizon and a little trigonometry give the height of the peak throwing it, and that is how the first lunar mountains were measured in 1610.Galileo had trained as an artist and understood shadows; he worked out that some peaks were several kilometres…Galileo, Sidereus Nuncius (1610)

#181Strange but trueWith no air to scatter light, the Moon has no twilight. The Sun goes below the horizon and the landscape goes out.On Earth the sky stays lit for the better part of an hour after sunset because the atmosphere above you is still…Apollo Lunar Surface Journal; NASA Moon facts

The Last Quarter

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The Last Quarter

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