The week of December 28 – January 3 takes us from Lunar Day 14 to 20. This week we will highlight the craters Proclus and Aristillus.

moon craters Aritillus and ProclusAristillus: [NE/F10] We were first introduced to Aristillus on Day 7 when its more complex features (ramparts, central mountain peaks, terraces, etc.) were conspicuous because of the low sun angle. We can now see that Aristillus is also at the center of a ray system, which means that the crater is less than a billion years old – a mere youngster in lunar terms!

Mare Crisium on the moonProclus: [NE/H14] Proclus is a small crater located just west of Mare Crisium. In spite of its size, it is one of the brightest spots on the Moon. When you view it around full Moon, you will notice it also has a system of rays that delicately fan out in a telltale butterfly-wing pattern, which tells you a lot about the flight path of the incoming projectile. Proclus is one of the best examples of what happens during a low-angle impact.


As I mentioned in last week’s Blog, Jupiter & Saturn are the closest they have been in 396 years. Here is an astonishing photo of their conjunction from Guatamala over an exploding volcano (from APOD)…

Jupiter and Saturn Conjuction from Guatamala over an exploding volcano


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
Moon Craters Proclus and Aristillus
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