The week of November 1-7 takes us from Day 26 to Day 3. This week we will highlight the moon crater Hevelius and the lunar basin Grimaldi located near the western limb of the Moon and viewable before sunrise on Tuesday morning.

lunar basin GrimaldiGrimaldi has a very dark floor and several LTP’s (Lunar Transient Phenomena) have been reported here, so be on the lookout. You might get lucky!

lunar basin Grimaldi is the darkest spot on the moonGrimaldi: [SW/K3; L=68°W] In comparison to Aristarchus (Day 11), which is the brightest spot on the Moon, Grimaldi is the darkest. Sunrise & sunset over Grimaldi is quite a lovely sight. The rim around Grimaldi has been heavily eroded by subsequent impacts, but once the floor is illuminated you will see quite a number of small craters, mounds, spots, streaks, and wrinkle ridges. LTP’s have also been spotted in the region, and some observers have reported being able to see a St. Andrew’s Cross emblazoned on the west wall. Grimaldi, in spite of its diameter of 143 miles, is a genuine basin, and if you look closely you might be able to trace out vestiges of an external ring.

Hevelius: [NW/J3; L=68°W] Hevelius is a large 66-mile moon crater just north of Grimaldi on the western shore of Procellarum. It is a moderately complex object with terraced walls that rise to 6,000 feet, a central hill, at least seven internal craters (how many can you see?) and a system of crisscrossing rilles that require a very low angle sun to become visible. Can you tell if the simple crater just in from the NW rim has a flat or rounded floor?


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 Crater Hevelius and Lunar Basin Grimaldi is the Darkest Spot on the Moon

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