IWLOP #083 - Rupes Recta
The famous "Straight Wall" is one of the most interesting features on the Moon.
Location: 22.0 S 7.0 W Origin: Tectonic Length: 110 km Rukl: 54 Type: Scarp
Objects: Rupes Recta, Birt, Promontorium Taenarium, Birt A, Rima Birt
Others Identified: Nicollet, Thebit, Thebit A
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Observation 1: Variable high clouds. R1: The Straight wall was barely visible.R2: The crater Birt in Mare Nubium to the west was easily identified. R3: Promontorium Taenarium was very large - 1/4 as long and almost as long (east to west) as the Wall. The curve of the peaks made it look like a wall of a much larger crater (now gone). |
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Observation 2: C1: Birt and Birt A were easily identified adjacent to the Wall. The shadow extended just west of Birt almost perfectly parallel to the Wall. Because this part was near the terminator, I could see the worn down crater wall (refer to note). Rimae Birt ran parallel to the Wall, running north of Birt; it was about half the length of the Wall. NOTE: (July 4/21) It always strikes me that there had been a large crater in this section of Mare Nubium because of the hint of a circular wall in the Mare floor. |
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Observation #3: This is not the best photo possible. It was taken using my iPhone mounted on the eyepiece with a NexYZ while doing a general 'look' at the Moon. The straight line defining the lit area from a dark area of Mare Nubium is Rupes Recta aka the Straight Wall! It's the absolute best example of a lunar fault. 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. Thebit (circular crater with most of its floor in darknesss, Thebit A, the small Thebit L beside A, Thebit J nested beside Thebit, and Rupes Recta! Thebit A appears to have impacted both Thebit and Thebit L. The crater Birt is the illuminated crater in the shadows. Promontorium Taenarium was very large and well illuminated at the south end of the Wall; an intermittent ridge line ran from Thebit J to the south end of Rupes Recta, creating what looked like a break in the Wall just before the Promontorium. Alpetragius is the small crater in the upper right, lying to the side between what you can see of the rims of Arzachel and Alphonsus. The bowl of the crater is in darkness but its rim is well illuminated. Had the floor been lit, you would have seen the central peak that takes up about 1/3 of the floor; this has lead to it being referred to as "egg in the nest". |