Moon Phases

First quarter moon appears half-illuminated

Half illuminated moon at 1st quarter.
View at EarthSky Community Photos. | Mohamed Mohamed of Tripoli, Libya, captured this great image of the first quarter moon on January 28, 2023. Thank you, Mohamed!

First quarter moon

Here are the characteristics of a first quarter moon:

– It’s the moon phase halfway between new moon and full moon.

– It’s a waxing moon.

– As viewed from anywhere on Earth, a first quarter moon appears at its highest in the sky at sunset. It rises around noon and sets around midnight.

– It’s called a quarter moon, but, from Earth, it looks half-illuminated, like half a pie. Or you might say that – at first quarter moon – we’re seeing half the moon’s day side or a quarter of the whole moon.

Half-lit Earth from north, and half-lit moon with divisions between dark and light sides lined up.
As seen from the north side of the moon’s orbital plane, the terminators (lines between sunny and shadowed sides) of the Earth and moon align at first quarter moon, and only the near half of the moon’s day side is visible from Earth. Image via Wikipedia Commons. Click here to see the animation.

Quarter moon? Half moon?

There’s another reason we call this moon a quarter and not a half. It’s because it’s one quarter of the way around in its orbit of Earth, as measured from one new moon to the next.

And what about the term half moon? That’s a beloved term, but not an official one.

Do you have access to a small telescope? Here are some telescopic sights to see on a first quarter moon:

Rupes Recta, or The Straight Wall, is best found on 8 days past new moon when the terminator falls across it.
View at EarthSky Community Photos. | Tom Wildoner in Weatherly, PA, captured this photo of Rupes Recta on January 14, 2019. He wrote: “Rupes Recta, a linear fault line, or rille, appears as a straight shadow during the first quarter phase of the moon giving it the nickname the Straight Wall. This fault has a length of about 68 miles (110 kilometers). The small (11 miles wide) crater Birt lies just to the west.” Thank you, Tom!
A moon just past 1st quarter, with Lunar X annotated.
View at EarthSky Community Photos | For those of you with telescopes, or telescopic lenses, here’s something to watch for on a moon near 1st quarter. Tim Yacyshyn in Richmond, British Columbia, Canada captured this image on October 5, 2019. He wrote: “Taken exactly 12 hours after 1st quarter. As you can see, the famous Lunar X stands out quite prominently.” Thank you, Tim!
First quarter moon, juxtaposed with a telescopic view of the moon at this phase.
View at EarthSky Community Photos. | Composite image of a moon nearly at 1st quarter with some of the features you can see on the moon at this phase – captured April 30, 2020 – by our friend Dr Ski in the Philippines. He wrote: ” … 10 hours before 1st quarter and the Lunar V and Lunar X are well defined … ” Thank you Dr Ski!

More articles about moon phases

As the moon orbits Earth, it changes phase in an orderly way. Follow the links below to understand the phases of the moon.

New moon
Waxing crescent moon
First quarter moon
Waxing gibbous moon
Full moon
Waning gibbous moon
Last quarter moon
Waning crescent moon

Bottom line: The first quarter moon occurs halfway between new moon and full moon. One quarter of the moon is visible from Earth, meaning that you see half of the daylit side of the moon, looking like half a pie.

Read more: Top 4 keys to understanding moon phases

Check out EarthSky’s guide to the bright planets

January 1, 2023
Moon Phases

Like what you read?
Subscribe and receive daily news delivered to your inbox.

Your email address will only be used for EarthSky content. Privacy Policy
Thank you! Your submission has been received!
Oops! Something went wrong while submitting the form.

More from 

Deborah Byrd

View All