How To See 'Lunar X' on the Moon Tonight

Lunar enthusiasts can catch a glimpse of the "Lunar X" tonight, a striking criss-cross shape on the moon that can only be seen in the hours around its first quarter phase. The unique, 50-mile-wide X shape is expected to appear on the moon tonight, March 6, from around 6:25 p.m. CST and will be visible for about four hours. The phenomenon results from a combination of light and shadows that create the illusion of a letter X appearing on the rim of the moon's Blanchinus, La Caille and Purbach craters. The X mark is easily visible using binoculars or a small telescope, says NASA. The space agency explains: "Near the Moon's first quarter phase, an astronaut standing close to the craters' position would see the slowly rising Sun very near the horizon. "Temporarily, crater walls would be in sunlight while crater floors would still be in darkness. "Seen from planet Earth, contrasting sections of bright walls against the dark floors by chance look remarkably like an X."

Timing is important when it comes to spotting the "Lunar X" and it takes around 2.3 hours for the X mark to form, astronomer Pete Lawrence noted in BBC Sky at Night magazine. Lawrence advised that low to medium magnification works best for observing Lunar X, "as this is less likely to emphasize the roughness created by smaller craters along the arms of the X." The X remains visible for about an hour after it's formed and will take a further 70 minutes to fade back into the surface of the moon as it slowly illuminates. So, in total, the window for spotting Lunar X is about 4.5 hours, he noted. A certain amount of luck is required to spot Lunar X, as the moon needs to be above the horizon during the visibility window and the weather needs to be right. Lawrence said that "it is often stated that the X is visible at the first quarter moon phase but, being visible for such a short period, greater precision is necessary." Moving your gaze further north from Lunar X will also allow you to spot Lunar V, which is formed by an illumination of the Ukert crater and several other smaller craters. Do you have a tip on a science story that Newsweek should be covering? Do you have a question about the moon? Let us know via science@newsweek.com.