Mons Rümker dome on the moonThe week of October 2-8 takes us from Day 12 to Day 18, spanning the full moon. This week we will highlight Mons Rümker, visible on Monday night. (This was featured in the 5/22/17 Blog, but it could only be seen in the early hours just before dawn.)

Mons Rümker dome on the moonMons Rümker: [NW/E4] Unfortunately this feature is too close to the Moon’s limb to see it very clearly, so coordinate your viewing with a favorable libration (which will be the case on Monday night). In spite of its name, Mons Rümker is not really a mountain, it’s an extensive complex of domes, so the low-lying Sun on Monday evening should help bring them out. The diameter of the formation is over 40 miles. Although there are about a dozen domes here, through a telescope it looks like a mound with a bumpy surface. Several of the domes have summit pits. Can you make any of them out?


Venus and Mars are in conjunction in the pre-dawn hours of Thursday morning. They are only about ¼° apart. It may be difficult to separate them naked eye because of the brightness of Venus, so use binocs or a low-power telescope.


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
Mons Rümker: Extensive Complex of Domes on the #Moon

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