Kitt Peak Nightly Observing Program
Splendors of the Universe on YOUR Night!
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Aristarchus and Herodotus
Aristarchus is not a particularly large crater, but it manages to stand out as an extremely bright crater. Near the northwestern limb of the Moon, Aristarchus is more reflective than the darker Oceanus Procellarum surrounding it. Nearby crater Herodotus is similar in size, but different in appearance. Herodotus is shallower and darker.
Copernicus is a large, conspicuous crater located in the Oceanus Procellarum (Ocean of Storms). It has extensive rays of ejecta spanning hundreds of kilometers from the rim of the crater. This crater is likely to be only hundreds of millions of years old—young for a lunar crater.
Gassendi is a large, 110 km wide, easy to recognize crater on the northern rim of the Mare Humorum. Gassendi and smaller crater Gassendi A together form a sort of ring-with-gemstone shape, making it easy to pick out the pair amongst all the other craters in the SW quadrant of the Moon. The floor of Gassendi is not very deep, and heavily fractured. Its central peaks are easy to see.
Hansteen and Billy
These two craters are nearly identical in size, but not in most other ways. Hansteen has terraced walls and a fractured floor, while Billy has a smooth, flooded floor. Though they are near the limb and somewhat foreshortened, they are a good pair to demonstrate contrasting crater features.
Kepler is one of the most conspicuous craters on the Moon, though it is one of the smaller more conspicuous craters. It has lengthy, bright rays, small central peaks, and slumps of material at the base of its walls. It looks rather like a mini-me of larger crater Copernicus (to its east). Though similar in diameter, it is much deeper than nearby crater Encke
Mairan is a crater located near the northwestern limb of the Moon, in a highland peninsula. To its east is the Mare Imbrium and to its west is the Oceanus Procellarum. It looks elongated, because it is near the limb of the Moon, but is a regular, circular crater. Nearby Mairan T is a lunar dome with steep walls and an oddly shaped crater at its peak.
Schickard is one of the largest craters on the near side of the Moon. Near the southwestern limb of the Moon, it appears elongated due to foreshortening. The floor of Schickard varies in brightness, with a large bright patch in the center of the crater. It is thought that Schickard was first flooded with mare lavas, which look dark, and then the Orientale Basin impact event showered bright Highlands material onto parts of its floor, along with many small secondary craters.
Some craters on the Moon look elongated, because they are foreshortened, meaning we are seeing them at an angle. The closer the crater is to the limb of the Moon, the more foreshortened it is. Schiller, however, is actually an elliptical crater—very unusual. It’s hard to be sure how Schiller formed. Notice the linear ridges on one end of the elongated crater, dividing the floor in half, and the small crater on the opposite end, connected to schiller by a valley.
Rümker is actually a unique complex of a dozen or so overlapping lunar domes. Together, they make one big, bumpy dome, 73 km across. Like the typical, smaller dome, it is challenging or impossible to see unless the Sun is very low in the sky over it.
Mare Humorum is one of the smaller mare on the near side of the Moon. It is situated on the western hemisphere, south of Oceanus Procellarum. It is estimated to be about 3.9 billion years old, and is the site of one fo the Moon’s mascons. Mascons, short for mass concentrations) have slightly higher gravity than the are around them. Mare Humorum has some striking ridges and rilles. A prominant crater, Gassendi interupts the northern “coast” of Mare Humorum—its floor cracked with many rilles. Yet another, smaller crater interupts Gassendi’s northern rim—creating a memorable figure of a ring with gemstone.
The Mare Imbrium Impact Basin formed when a large object crashed into the Moon 3.9 billion years ago. subsurface lava rose to flood the giant crater, eventually solidifying into a younger, smoother terrain. Prominent features of Mare Imbrium include the crater Plato to the north, with a dark crater floor; Sinus Iridum (meaning Bay of Rainbows) to the northwest, with the Montes Jura mountain range forming a distinct C-shaped knob on the edge of the mare; and the 3 mountain ranges—Montes Alpes, Caucasus, and Apenninus—that mark the eastern edge of the mare.
Also known as a twilight zone, a terminator is where the shadow of night and the light of day come to meet on a planetary body. At the edge of where the Sun’s light reaches, the terminator is constantly moving as the Moon rotates. When observing the Moon, many features are best observed when they are near the terminator, where shadows are long and plentiful. The shadows provide higher contrast between surface features.
This is the largest sinuous rille on the Moon. It is about 3 km wide at its western end, and widens up to 6 km toward the eastern end, where you will find the Cobra Head. The Cobra Head is a steep volcanic depression near the top of a mountaid at the end of the snake-like sinuous rille. Shcröter’s Valley may have been a major source of the lava that formed the Oceanus Procellarum.Schröter’s Valley is part of the Aristarchus Plateau, and is foundto the immediate northwest of the small, but very bright crater Aristarchus.
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Nightly Observing Program. Most of the above images were taken as
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