Wondering why the moon looks smaller this evening? It’s due to us being on day 19 of the lunar cycle.

The lunar cycle is made up of eight separate phases concerning the moon’s visibility. This cycle spans roughly 29.5 days, as per NASA, and these phases arise as the Sun lights up various areas of the moon during its orbit around Earth.

Let’s explore what’s going on with the moon tonight, Sept. 11.

What is the moon phase for today?

On Thursday, Sept. 11, the moon is in a Waning Gibbous phase, appearing 81% illuminated from our perspective on Earth, according to NASA’s Daily Moon Observation.

There’s plenty to observe tonight when you gaze upwards. Without any tools, appreciate views of the Oceanus Procellarum, Mare Vaporum, and Mare Tranquillitatis.

If you have binoculars handy, you can also catch sight of the Grimaldi Basin, Posidonius Crater, and Mare Frigoris. With a telescope, you’ll be able to view Reiner Gamma, Apollo 16, and the Caucasus Mountains.

When will the next full moon occur?

The upcoming full moon is set for Oct. 6. The previous full moon took place on Sept. 7.

What are the phases of the moon?

As per NASA, moon phases result from the 29.5-day orbital cycle of the moon, which changes the angles formed between the Sun, Moon, and Earth. Moon phases describe how the moon appears from our vantage point on Earth as it revolves around us. We always see the same face of the moon, but the portion illuminated by the Sun varies depending on its orbital position. This leads to full moons, half moons, and moons that are virtually invisible. There are eight primary moon phases, following a cyclic pattern:

New Moon – The moon lies between Earth and the sun, making the side facing us dark (invisible).

Waxing Crescent – A narrow crescent of light appears on the right side (Northern Hemisphere).

First Quarter – The right half of the moon is illuminated, resembling a half-moon.

Waxing Gibbous – Over half is lit, but it has not yet reached fullness.

Full Moon – The complete surface of the moon is lit up and fully visible.

Waning Gibbous – The moon starts to lose light on the right side.

Last Quarter (or Third Quarter) – Another half-moon phase, but the left side is illuminated this time.

Waning Crescent – A slender sliver of light persists on the left side before fading back into darkness.