The 8 Moon Phases Explained

The four primary phases — New, First Quarter, Full, and Last Quarter — mark the cycle's turning points. The four intermediate phases — the crescents and gibbous Moons — describe the gradual change in between. Phase descriptions below use the Northern Hemisphere view; in the Southern Hemisphere the lit side appears mirrored.

1. New Moon

At New Moon, the Moon sits roughly between Earth and the Sun, so its sunlit side faces away from us. The disc is essentially dark and rises and sets with the Sun, which is why it's so hard to spot. This is the official start of a new lunar cycle, with illumination near 0%.

2. Waxing Crescent

A day or two after New Moon, a slim crescent of light appears on the right edge (in the Northern Hemisphere). "Waxing" means the lit area is growing. You'll often catch a waxing crescent low in the west just after sunset. Sometimes the rest of the disc glows faintly — that's earthshine, sunlight reflected from Earth onto the Moon.

3. First Quarter

About a week into the cycle, exactly half of the visible disc is lit — the right half from the Northern Hemisphere. It's called "first quarter" because the Moon has traveled a quarter of the way around Earth, not because a quarter is lit. A first-quarter Moon is high in the sky at sunset, making it convenient for early-evening viewing.

4. Waxing Gibbous

"Gibbous" describes a Moon that is more than half but not yet fully lit. As the waxing gibbous brightens night by night, it heads toward Full. The Moon now rises in the afternoon and is visible for most of the night.

5. Full Moon

At Full Moon, Earth lies between the Sun and Moon, so the entire near side is lit — illumination near 100%. The Full Moon rises around sunset and sets around sunrise, dominating the night sky. It's the brightest phase, though paradoxically not the best for seeing crater detail, because shadows are shortest when sunlight hits the surface straight on.

6. Waning Gibbous

After Full, the lit portion begins to shrink — "waning." The waning gibbous still appears large and bright, but a sliver of darkness now creeps in from the right. It rises later each night, often after dark.

7. Last Quarter

Also called the third quarter, this is the mirror image of First Quarter: half the disc is lit, but now it's the left half (Northern Hemisphere). A last-quarter Moon rises around midnight and is high in the sky at dawn. Like First Quarter, it's a great time to observe craters along the terminator.

8. Waning Crescent

The final phase is a thin, shrinking crescent on the left, visible in the eastern sky before sunrise. As it fades, the Moon approaches the Sun again in our sky — and once the lit side turns fully away from us, we're back to New Moon and the cycle begins anew.

Putting it together

From New to Full the Moon waxes (grows); from Full back to New it wanes (shrinks). The whole sequence is driven by one thing: the changing angle between the Sun, Earth, and Moon as the Moon orbits us. Once that clicks, you can glance up on any clear night and read roughly where in the cycle the Moon is.