Rupes Recta is a linear fault on the Moon, in the southeastern part of the Mare Nubium. The name is latin for "Straight Fault", although it is more commonly called the Straight Wall. This is the most well-known escarpment feature on the Moon, and is a popular target for amateur astronomers.When the sun illuminates the feature at an oblique angle at about day 8 of the lunar orbit, the Rupes Recta casts a wide shadow that gives it the appearance of a steep cliff. The fault has a length of 110 km, a typical width of 2-3 km, and a height of 240-300 m. Thus although it appears to be a vertical cliff in the lunar surface, in actuality the grade of the slope is relatively shallow.
To the west of this escarpment is the Birt crater, which is about 10.5 miles in diameter. Also to the west is the Rima Birt rille. At the southern end is a group of hills often called the "Stag's-Horn Mountains", although this name is not officially recognized by the IAU.
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Oblique view from Apollo 16 mapping camera.
