The moon takes about 29.5 days to cycle from new moon through full moon and back again. This is called a synodic month.The moon doesn't produce its own light — it reflects sunlight. As the moon orbits Earth, the relative positions of the sun, Earth, and moon change, altering how much of the moon's illuminated side we can see. This is what causes the moon's phases.
8 Moon Phases
New Moon
Invisible yet present, the moon catches its breath
The moon is positioned between Earth and the sun, so its illuminated side faces away from us. This makes it virtually invisible in the sky.
ObservationCannot be observed with the naked eye. This is also when solar eclipses can occur.
CultureMarks the 1st day of the lunar calendar and symbolizes new beginnings. In East Asian culture, this day was considered the start of a new month.
Waxing Crescent
A silver eyebrow gently drawn across the night sky
The moon has moved about 45 degrees east of the sun, creating a thin crescent shape. Sunlight illuminates only the right edge, forming an eyebrow-like sliver.
ObservationVisible for 1-2 hours in the low western sky just after sunset.
CultureAppears around the 2nd-3rd day of the lunar month. Traditionally, people made wishes upon seeing the crescent moon.
First Quarter
A half-open door of night, moving toward the light
The moon is 90 degrees from the sun, illuminating exactly half its face. The right half is bright and the left half is dark, forming a D-shape.
ObservationObservable in the southern sky from afternoon until midnight. Highest at sunset.
CultureFalls around the 7th-8th day of the lunar month. The terminator line reveals craters most clearly, making it ideal for telescope observation.
Waxing Gibbous
Swelling with anticipation toward fullness
More than three-quarters of the moon is illuminated, approaching full moon. Only a slight shadow remains on the left edge.
ObservationRises in late afternoon and illuminates the sky until dawn.
CultureAround the 11th-12th lunar day, anticipation builds before the full moon. The moonlight is bright enough for outdoor activities.
Full Moon
A perfect light illuminating the whole world
The moon is directly opposite the sun, with its entire illuminated face turned toward Earth. This is the brightest lunar phase.
ObservationRises in the east at sunset and crosses the sky throughout the night, setting in the west at dawn.
CultureFalls on the 15th day of the lunar month — the day of Chuseok and the Lunar New Year's first full moon festival. Symbolizes abundance and completion.
Waning Gibbous
Slowly retreating light, the lingering afterglow
After the full moon, the left side gradually darkens. Shadows begin to appear on the right edge, though more than three-quarters remains bright.
ObservationRises late at night and is visible until morning. Best for dawn observation.
CultureAround the 18th-19th lunar day, a time to savor the afterglow of the full moon. Ancient poets wrote of impermanence while gazing at the waning moon.
Last Quarter
Quiet reflection in the waning light
The moon is 270 degrees from the sun, illuminating exactly half — the opposite of the first quarter. The left half is bright and the right half is dark.
ObservationRises after midnight and is visible in the morning sky. Observable in the early morning hours.
CultureFalls around the 22nd-23rd lunar day. Only visible at dawn, it's sometimes called the 'dawn moon.'
Waning Crescent
A last smile awaiting the dawn
As the moon approaches the sun again, a thin crescent appears on the left side. It's preparing to disappear into the new moon phase.
ObservationVisible briefly in the eastern sky just before sunrise at dawn.
CultureAround the 27th-28th lunar day. The word 'Geumuem' in Korean comes from 'to hide,' as the moon hides itself during this phase.
Special Phenomena
Supermoon
When the full moon coincides with the moon's closest approach to Earth, appearing up to 14% larger and 30% brighter than usual.
Cause
The moon's orbit is elliptical, not perfectly circular. When a full moon occurs at perigee (closest point), it becomes a supermoon.
Frequency
Occurs 3-4 times per year, with the closest one being called 'the supermoon of the year.'
Lunar Eclipse
Earth's shadow falls across the moon. During a total lunar eclipse, the moon takes on a reddish hue, earning it the nickname 'Blood Moon.'
Cause
When the sun, Earth, and moon align, Earth's shadow is cast on the moon. Red light filtered through Earth's atmosphere reaches the moon, creating the red appearance.
Frequency
Occurs 0-3 times per year. A total lunar eclipse is visible from any given location about once every 2.5 years.
Blue Moon
When two full moons occur in a single calendar month, the second is called a Blue Moon. It doesn't actually appear blue.
Cause
The lunar cycle (29.5 days) is shorter than a calendar month (30-31 days), so occasionally two full moons fit within one month.
Frequency
Occurs roughly once every 2.7 years. The expression 'once in a blue moon' means 'very rarely.'
Harvest Moon
The full moon closest to the autumn equinox (around September 23). It rises earlier than usual, providing bright moonlight throughout the evening.
Cause
In autumn, the difference in moonrise times between successive nights is smaller, allowing several consecutive nights of bright moonlight shortly after sunset.
Frequency
Occurs once a year, around the autumn equinox. Farmers historically used this moonlight to harvest crops late into the evening.
Observation Tips
1The full moon rises in the east at sunset. Near the horizon, it appears especially large due to the 'moon illusion.'
2The crescent and waning crescent moons are only briefly visible around sunrise or sunset, so timing is key.
3Along the first quarter moon's terminator line, craters and mountain ranges are most clearly visible.
4Clear weather is essential for moon observation. Choose nights with low humidity and no clouds.
5Escape the city's light pollution for the suburbs, where you can even see shadows cast by moonlight.
6The moon repeats the same phase roughly every 29.5 days. This is called a synodic month.