Here’s how to see the Lunar X and V at 1st-quarter moon

View at EarthSky Community Photos. | Frank Lu of Texas captured this image on February 5, 2025, and wrote: “Inspired by Deborah Byrd’s article in EarthSky’s Astronomy Essentials, I went out looking for the Lunar X and Lunar V on this 1st-quarter moon. I’m extremely pleased to find them.” Thank you, Frank!

Tonight’s 1st quarter moon is a perfect time to look for the Lunar X and V. It occurs overnight tonight at 2:32 UTC on April 24. So take a look!

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Lunar X and Lunar V

Have you heard of Lunar X and Lunar V? They are famous optical features on the moon, visible through telescopes. So, when the moon’s terminator – or line between light and dark on the moon – is located in just the right place, you can see a letter X and a letter V on the moon’s surface. Are they a sign of an alien visitation? No. Rather, Lunar X is a great example of how lighting and topography can combine on a planet or moon to produce a pattern that seems familiar to the human eye.

In reality, the illusion of Lunar X is created by sunlight falling on the rims/ridges between the craters La Caille, Bianchini and Purbach. And the V is caused by light illuminating crater Ukert, along with several smaller craters.

View at EarthSky Community Photos. | Kannan A in Singapore wrote on April 19, 2021: “Upon a close look at the moon tonight, I realized that the Lunar X and Lunar V were clearly visible. These are transient lunar features visible on the lunar surface for about 4 hours once a month. They are most striking when they are visible on the shadow side of the terminator. But they will remain visible against the lunar surface even after the terminator has moved because they are brighter than the surrounding area.” Thank you, Kannan!

When are they visible?

Basically, people see Lunar X and Lunar V at each cycle of the moon, but only for a short time. In fact, they’re observable for about four hours around the 1st quarter moon phase.

What’s the current moon phase? Check EarthSky’s visible planets and night sky guide.

View at EarthSky Community Photo. | Greg Redfern captured this image from Virginia on July 2, 2025, and wrote: “The lunar X & V showed up last night in great splendor … what a treat to see and image.” Thank you, Greg!

View at EarthSky Community Photos. | Matthew Chin from Hong Kong, China, shared this image of the moon, where Lunar X and Lunar V are visible, on January 18, 2024. Thank you, Matthew!

Bottom line: Lunar X and Lunar V are optical features on the moon. They are visible through a telescope for several hours around the time of the 1st quarter moon.

The post Here’s how to see the Lunar X and V at 1st-quarter moon first appeared on EarthSky.

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View at EarthSky Community Photos. | Frank Lu of Texas captured this image on February 5, 2025, and wrote: “Inspired by Deborah Byrd’s article in EarthSky’s Astronomy Essentials, I went out looking for the Lunar X and Lunar V on this 1st-quarter moon. I’m extremely pleased to find them.” Thank you, Frank!

Tonight’s 1st quarter moon is a perfect time to look for the Lunar X and V. It occurs overnight tonight at 2:32 UTC on April 24. So take a look!

You deserve a daily dose of good news. For the latest in science and the night sky, click here to subscribe to our free daily newsletter.

Lunar X and Lunar V

Have you heard of Lunar X and Lunar V? They are famous optical features on the moon, visible through telescopes. So, when the moon’s terminator – or line between light and dark on the moon – is located in just the right place, you can see a letter X and a letter V on the moon’s surface. Are they a sign of an alien visitation? No. Rather, Lunar X is a great example of how lighting and topography can combine on a planet or moon to produce a pattern that seems familiar to the human eye.

In reality, the illusion of Lunar X is created by sunlight falling on the rims/ridges between the craters La Caille, Bianchini and Purbach. And the V is caused by light illuminating crater Ukert, along with several smaller craters.

View at EarthSky Community Photos. | Kannan A in Singapore wrote on April 19, 2021: “Upon a close look at the moon tonight, I realized that the Lunar X and Lunar V were clearly visible. These are transient lunar features visible on the lunar surface for about 4 hours once a month. They are most striking when they are visible on the shadow side of the terminator. But they will remain visible against the lunar surface even after the terminator has moved because they are brighter than the surrounding area.” Thank you, Kannan!

When are they visible?

Basically, people see Lunar X and Lunar V at each cycle of the moon, but only for a short time. In fact, they’re observable for about four hours around the 1st quarter moon phase.

What’s the current moon phase? Check EarthSky’s visible planets and night sky guide.

View at EarthSky Community Photo. | Greg Redfern captured this image from Virginia on July 2, 2025, and wrote: “The lunar X & V showed up last night in great splendor … what a treat to see and image.” Thank you, Greg!

View at EarthSky Community Photos. | Matthew Chin from Hong Kong, China, shared this image of the moon, where Lunar X and Lunar V are visible, on January 18, 2024. Thank you, Matthew!

Bottom line: Lunar X and Lunar V are optical features on the moon. They are visible through a telescope for several hours around the time of the 1st quarter moon.

The post Here’s how to see the Lunar X and V at 1st-quarter moon first appeared on EarthSky.

from EarthSky https://ift.tt/K8FHZLJ