The week of November 27 – December 3 takes us from Day 16 to Day 21. This week we will highlight Rima Hyginus (the Hyginus rille) on the moon, viewable on Saturday night around 11:00 and located in the NE quadrant of the Field Map at J10.

Rima Hyginus - the Hyginus rille on the moonRima Hyginus: [NE/J10; L=8°E] At the west end of the Ariadaeus rille on the moon, there is a narrow diagonal shunt that connects Ariadaeus to Rima Hyginus. This new rille parallels Rima Ariadaeus for about 20 miles, then continues west until it encounters the small 6-mile crater Hyginus. At that precise point, it changes direction and veers northward toward Mare Vaporum. The fact that Hyginus crater is located precisely at the pivot point is a curiosity. Can this just be coincidence?

Rima Hyginus is 2.5 miles wide and is easily seen in very small telescopes. It is really made up of a line of linked craters which are best seen just northwest of the moon crater Hyginus. With good optics and steady seeing you might be able to make some of these out even with a three-inch scope. Wood suggests that these are actually rimless collapse pits of internal origin and that the crater Hyginus (also rimless) might be one of their number. Can you see any of the individual craters, or does Rima Hyginus just look like a linear feature?


On December 2, 1971, the Mars 3 was the first craft to soft-land on Mars.


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
Rima Hyginus (Hyginus Rille) on the Moon
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