The week of February 24 – March 1 takes us from Lunar Day 1 to Day 7. This week we will highlight a feature popularly referred to as the Lunar X.

Lunar X: [SE/M10] On Sunday evening, the Sun will light up the mountain peaks immediately to the west of the crater 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, as will be the case on Sunday evening. Once it has formed, the image will last only for about three hours. 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. I am indebted to Dana Thompson for permission to use his photo of the Lunar X.)Photo of Lunar X by Dana Thompson


Betelgeuse update: In spite of the changes that Betelgeuse is undergoing, scientists now tell us they are not (alas) harbingers of an impending supernova explosion. Although Betelgeuse will go supernova at some time, it may not happen for a million years, so don’t hold your breath.

There is some confusion about how to pronounce its name. I prefer “bet-el-jewz” but since the movie Beetlejuice came out in 1988 that’s how most people pronounce it.


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 “X” in the Sky: Lunar X
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