The week of June 12-18 takes us from Day 25 to Day 1.

This week we will highlight the rille Rima Marius on the moon (in the NW quadrant of the Moon Map at H5) and viewable early Tuesday morning.

Rille Rima Marius on the MoonRima Marius: [NW/H4-5] Just to the northwest of the moon crater Marius C is Rima Marius, a sinuous rille that extends for 150 miles. When the rille starts out, it is about 1.2 miles wide (~1 arc-second), but it tapers down to only 0.3 miles. Because a line can be easily distinguished when a point of the same diameter is totally invisible, you should be able to see the rille when its width is well below the theoretical limits of your telescope. See how far you can extend Rima Marius across the lunar surface.


On Wednesday, Jupiter is 1.5° south of the Moon, and on Friday, Mercury is 4° south of the 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
Rille Rima Marius on the Moon

Leave a Reply

Your email address will not be published. Required fields are marked *