The joy of capturing a clear image of the moon through a telescope is unmatched. Almost a decade ago, I experienced this thrill for the first time with a very basic setup. Holding my phone camera up to the eyepiece, I managed to get a few fuzzy images before finally capturing a clear picture of the moon’s surface. Little did I know at the time, but I had stumbled upon a rare phenomenon known as the lunar X and V.
The lunar X and V are optical illusions that appear on the moon’s surface during a specific 4-to-6-hour window each month. These features are created by the way sunlight hits the rims of certain craters when the moon is in its first quarter phase. The terminator, the line between light and shade on the moon, plays a crucial role in making these illusions visible.
The lunar X is a bright X-shaped formation that emerges when light falls on the rims of craters named La Caille, Blanchinus, and Purbach. On the other hand, the V appears due to the way light hits a crater called Ukert and surrounding smaller craters. To witness these phenomena, a telescope is necessary, along with perfect timing.
The upcoming first quarter moon on 26 January will provide a chance to observe the lunar X and V. However, the visibility of the moon and these illusions will depend on your location. For instance, in New York, the best time to view them will be around midnight on the night of 25 January. Software like Stellarium can help you determine when and where the moon will be visible from your location.
Mark your calendars for the upcoming first quarters on 24 February, 25 March, and 24/25 April to catch a glimpse of the lunar X and V. For UK residents, 25 March is a favorable date as the first quarter will occur around 7pm local time. The alignment of various factors for these illusions to be visible makes the experience even more special.
As I reflect on my first encounter with the lunar X and V, I feel incredibly fortunate to have captured these fleeting tricks of light. The beauty and mystery of the moon never cease to amaze, making each observation a unique and rewarding experience.
For more intriguing articles like this, visit newscientist.com/maker. Stay updated with Abigail Beall, the specials editor at New Scientist and author of The Art of Urban Astronomy, by following her on Twitter @abbybeall.
