Get ready for a cool sight on the Moon! Around the First Quarter phase this week, a unique optical illusion makes it look like gigantic letters ‘X’ and ‘V’ are etched onto the lunar surface. It’s a fleeting phenomenon, often called a “clair-obscur” effect, where the play of sunlight and shadow creates familiar shapes on the rugged terrain.
This month, the First Quarter Moon happens late on July 2nd (or early July 3rd depending on your time zone). This specific timing and angle of sunlight are key to seeing these lunar letters. It’s a fun skywatching target that doesn’t require fancy equipment, though binoculars or a small telescope will definitely enhance the view.
Close-up view of the Moon's surface, highlighting the optical illusion of the Lunar X and Lunar V shapes created by sunlight and shadows.
What Are the Lunar X and V?
These aren’t actual markings on the Moon! The Lunar X and Lunar V are visual tricks caused by the angle of sunlight hitting specific craters at just the right moment. Think of it like finding shapes in clouds, but on a cosmic scale.
The ‘X’ is formed by sunlight illuminating the rims of several craters – Bianchini, Purbach, and La Caille – while the surrounding area is still in shadow. The ‘V’ appears nearby, created in a similar way by light catching part of the Ukert Crater. These effects are most dramatic along the terminator, which is the dividing line between the sunlit and dark sides of the Moon.
When and How to Spot Them
The best time to look for the Lunar X and V is typically for about four hours leading up to the First Quarter Moon phase. For observers in the Northern Hemisphere, the First Quarter occurs at 11:41 p.m. EDT on July 2 (which is 0341 GMT on July 3).
This means your prime viewing window is the evening of July 2nd, especially as the sun sets and the Moon becomes visible in the eastern sky. Look towards the terminator line on the right side of the half-lit Moon. The letters appear just on the dark side of this line, their upper parts just kissed by the sun. Keep watching over an hour or two – you’ll see them sharpen and then fade as the Moon’s rotation changes the lighting angle. If you miss them just before the First Quarter, they might still be faintly visible for a short time afterward as they cross into the sunlit side.
Do You Need a Telescope?
While the effect is sometimes glimpsed with strong binoculars, a small telescope is highly recommended to really see the shapes clearly. Even a basic 6-inch aperture telescope will reveal the details. If you have a larger scope, you’ll not only see the X and V but also the surrounding craters and rugged lunar landscape in impressive detail.
Detailed image of the Moon during its first quarter phase, showing the distinct Lunar X optical effect near the terminator line.
The Lunar X is found about 25 degrees south of the Moon’s equator, close to prominent craters like Werner and Aliacensis. The Lunar V is located less than 10 degrees above the equator, near the Ukert Crater. You don’t need to know the exact coordinates, though; just scan the terminator line on the night of July 2nd, and with a little patience, the shapes should become apparent.
A small amateur telescope, recommended for viewing celestial objects like the Moon and the Lunar X and V.
Seeing the Lunar X and V is a fun way to connect with the night sky and witness how light and shadow play across celestial bodies. It’s a reminder that even familiar objects like our Moon can hide fascinating visual phenomena.
Conclusion
Mark your calendars for the evening of July 2nd! The First Quarter Moon offers a brief, exciting chance to see the natural optical illusion of the Lunar X and V on the Moon’s surface. Grab your binoculars or a small telescope and look towards the terminator line. It’s a simple yet captivating astronomical sight that highlights the dynamic interplay of light and the Moon’s topography.
Looking to explore the night sky further? Check out guides on choosing the best telescopes or binoculars for getting started in skywatching.
