Lunar XThe week of April 16-22 takes us from Day 1 through Day 7. This week we will highlight an unusual feature called the Lunar X, visible on April 22nd.

Purbach Cross and the Werner XLunar X: [SE/M10] On Sunday evening (Around 6 days 22 hours depending on libration–you have to get this pretty exact, it’s a narrow window) as the terminator crosses Blanchinus, the Sun will light up the mountain peaks immediately to the west of Blanchinus and you will see a brilliantly lit “X” at the intersection of the rims of Blanchinus, La Caille, and Purbach. Look for it when the terminator is around 1°-2° east. Once it has formed, the image will last only for about three hours. (If you miss it, try again next month.) The formation is also known as the Purbach Cross and the Werner X. (Because it is not an officially recognized object, you will not find it listed on the Field Map.)


For a stunning virtual fly-over tour of the Moon that NASA has just released, click the link below:

NASA Releases Stunning HD Virtual Tour of Moon


It is highly recommended that you get a copy of Sky and Telescope’s Field Map of the Moon, the very finest Moon map available for use at the telescope. It is available for $10.95 at and on Amazon. All features mentioned in this blog will be keyed to the grid on the Field Map and will look like this: Plato: [NW/D9]

Courtesy of Gray Photography of Corpus Christi, Texas
Lunar photos: NASA / USGS / BMDO / LROC / ASU / DLR / LOLA / Moon Globe. Used by permission

Andrew Planck
Brilliantly Lit Lunar X on the Moon
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