Moon phase tonight: what to look for on December 20

Get ready, stargazers: tonight offers a perfect, moonless sky for observing stars and deep-sky objects.

On December 20, tonight, the moon is currently in its Waxing Crescent phase in the U.S., but it is 0% illuminated, making it effectively invisible.

However, in some parts of the world (depending on the time zone), the New Moon officially arrives tonight.

During this phase, the moon is too close to the sun in the sky to be visible, as it rises and sets with the sun and is absent from the night sky.

 According to NASA's daily guide, no lunar surface details will be visible. The last full moon occurred on December 4, 2025, and the next one will be on January 3, 2026.

What's the Waxing Crescent Moon phase?

According to NASA, the crescent phase of a moon begins when the illuminated half of the moon faces mostly away from Earth, with only a tiny portion visible to us from our planet.

It grows daily as the Moon’s orbit carries the moon’s dayside farther into view. Every day, the moon rises a little bit later.

How do moon phases work?

According to NASA, the moon takes around 29.5 days to complete one full lunar cycle.

Throughout this time, it passes through a series of phases as it circles the Earth.

Even though the moon always shows us the same side, its appearance changes because varying amounts of sunlight hit the side we see, making it look full, crescent, or new.

This process is divided into eight main lunar phases:

New Moon: This phase begins when the moon is between Earth and the sun, so the side we see is dark.

Waxing Crescent: It occurs when a small sliver of light appears on the right side (Northern Hemisphere).

First Quarter: A half phase of the moon is lit on the right side, and it looks like a half moon.

Waxing Gibbous: In this phase, more than half of the moon is lit up, but it’s not quite full yet.

Full Moon: This lunar phase begins when the entire face of the moon is illuminated and is fully visible from Earth.

Waning Gibbous: This is the phase when the moon begins losing light on its right side (in the Northern Hemisphere).

Third Quarter: It is also called another half-moon, but this time the left side is lit.

Waning Crescent: A moon phase when a thin sliver of light remains on the left side until it’s no longer visible.