A gibbous moon is a Moon that is more than half lit but not completely full. There are two of them in every cycle: the waxing gibbous, which comes between the first quarter and the full moon as the lit part grows, and the waning gibbous, which comes after the full moon, between full and the third quarter, as the light shrinks. The word comes from the Latin gibbus, meaning "hump," after the bulging, lopsided shape.
Waxing gibbous vs waning gibbous
They look almost identical, mirror images of each other, but they keep very different hours. Here's how to tell them apart from the Northern Hemisphere:
| Waxing gibbous | Waning gibbous | |
|---|---|---|
| Comes | After first quarter, before full | After full, before third quarter |
| Lit side | Right side, with a dark sliver on the left | Left side, with a dark sliver on the right |
| Changing | Growing a little each night | Shrinking a little each night |
| Rises | Mid to late afternoon | Mid to late evening |
| Best seen | Evening, in the south and east | After midnight and early morning, in the south and west |
| What comes next | Full moon | Third quarter |
The fastest test is the time. If you see a big, nearly round Moon in the early evening, it's waxing gibbous: it was already up before sunset and will set in the small hours. If it's high in the sky at dawn, or hanging in the west on your morning commute, it's waning gibbous.
In the Southern Hemisphere, the lit sides swap: a waxing gibbous is lit on the left and a waning gibbous on the right. The timing works exactly the same way. For the full sequence of phases, see moon phases in order.
When to look for a gibbous moon
The two gibbous phases are the easiest phases to catch without trying, because they're up for most of the evening or most of the morning.
A waxing gibbous rises in the afternoon, often while the Sun is still well up, so it's one of the best phases for spotting the Moon in daylight, low in the eastern sky. By nightfall it's well up in the south-east. Each evening it rises about fifty minutes later and looks a little rounder, until it reaches full and rises around sunset.
A waning gibbous rises after dark, a little later each night, and is at its highest in the hours before dawn. After sunrise it's still there, pale in the western sky, which is why so many people notice the Moon on a morning walk to school or work and wonder what it's doing up. We explain that daytime visibility in why can you see the moon during the day.
How long a gibbous moon lasts
Each gibbous phase lasts about a week. The waxing gibbous begins right after the first quarter, when the Moon is just over half lit, and ends at the instant of full moon, about seven days later. The waning gibbous runs for about the same time from full to the third quarter.
Across each of those weeks the lit part changes a lot, from just over half to nearly all of the disc. A gibbous moon a day before full can look perfectly round to the naked eye; you'd only notice the slightly flattened edge with binoculars. That's why many people think they've seen a full moon for three or four nights running. Strictly, only the moment of opposition counts as full, and the nights either side are gibbous. For the exact phase and how much of the Moon is lit tonight, check our moon phase today page.
Why a gibbous moon is the best one for binoculars
Oddly, the full moon is one of the worst times to look at the Moon's surface. At full, sunlight hits the near side head-on, there are no shadows, and the landscape looks flat and washed out, apart from the bright streaks of rays splashed around a few young craters.
A gibbous moon has a terminator, the line between day and night on the lunar surface. Along that line the Sun is low in the lunar sky, so mountains and crater rims cast long shadows, and the relief jumps out even in ordinary binoculars. On a waxing gibbous, the terminator is on the left (from the north) and moving across the surface night by night, so you see a slightly different strip of craters every evening.
A few tips:
- Steady the binoculars against a fence post or car roof, or lie back in a garden chair.
- Look along the shadow line, not at the bright middle.
- Come back the next night. The terminator will have shifted, and new features will be sitting in sunrise.
The word "gibbous" isn't only for the Moon, either. Astronomers use it for planets too. Mars never appears less than gibbous from Earth, and when Galileo saw Venus pass through crescent and gibbous phases through his telescope in 1610, it helped show that Venus orbits the Sun rather than Earth.
The gibbous phases in astrology and moon rituals
In moon practice, the two gibbous phases have opposite jobs, matching the direction of the light.
The waxing gibbous is the phase of refining. Whatever you started at the new moon is nearly ready, and this is the week to edit, rehearse, double-check and adjust, before the full moon shows the result. It suits patient, practical work rather than fresh starts.
The waning gibbous is often called the disseminating phase in astrology, from the idea of spreading something around. After the full moon's culmination, it's a time for sharing what you learned, teaching, thanking people and passing things on.
Astrologers also read the phase of the Moon at your birth. In the eight-phase system popularized by Dane Rudhyar, someone born when the Moon was between 135 and 180 degrees ahead of the Sun is a "gibbous phase" person, associated with analysis and improvement, while someone born in the later part of the waning gibbous stretch, between 225 and 270 degrees, is a "disseminating phase" person, associated with communicating and teaching. You can find your own in what moon phase were you born under, using the Sun and Moon positions from a free birth chart.
Questions readers ask
How do you pronounce gibbous?
GIB-us, with a hard "g" as in "gift." The word comes from the Latin for hump, and astronomers use it for any Moon or planet that is more than half lit.
Is a gibbous moon the same as a full moon?
No. A gibbous moon is more than half lit but not completely full. A day or two either side of the full moon it can look round to the naked eye, but there's still a thin unlit edge.
Can you see a gibbous moon during the day?
Yes, easily. A waxing gibbous rises in the afternoon and can be seen in the eastern sky before sunset, and a waning gibbous is often still visible in the western sky for several hours after sunrise.
Is a waxing gibbous moon good for manifesting?
In modern moon practice, the waxing gibbous is linked with refining and preparing rather than beginning, so it's seen as a good week to keep working on an intention set at the new moon. That's a tradition of reflection, not a rule, and the work itself does more than the timing.
