2010 10 17 – Rupes Recta
2010 10 16, 2351 UT – 2010 10 17, 0142 UT Rupes Recta
PCW Memorial Observatory, OH, USA, Erika Rix
Zhumell 16”, 20mm TV, 3x Barlow, 270x mag, 13% T moon filter
Temp: 7°C, 59% humidity, S: Antoniadi II, T: 2.5/6
Sketch created scopeside with Rite in the Rain paper and charcoal.
Phase: 65.2°
Lunation: 9.33d
Illumination: 70.9%
Lib. Lat: -3°50’
Lib. Long: +2°56’
Az: 209°37’, Alt: 32°06’
Rupes Recta: Scarp, 7.7° W, 22°S
Imbrian period (-3.8 billion yrs to –3.2 billion yrs)
Length: ~110 km, Height: 240-300 m, Apparent Width: 2.5 km
Located in Mare Nubium, this scarp, also known as the Straight Wall, was apparent by the shadow cast from illumination from the east. The shadow wasn’t very wide, but rather narrow and smudging to the west. The eastern side of it was crisp and sharp. During the waning phase, this same feature would appear as a white line from the illumination coming from the west. The slope incline is ~30-40° (ref. Virtual Moon Atlas). For a good comparison between the waning and waxing phases for this feature, please have a look at this site: Illumination comparison; Astrosurf.com
Lightened areas around Birt (Copernician period) made a path from the crater to the fault, showing off Birt A as well as a “V” shaped area nestled between Birt and the companion craters K, J, and H (you will have to look at an atlas for those craters as I wasn’t able to see them during my observation last night).
The ridges to the south of Rupes Recta formed what I always pictured as a scoop, make the ridge and the fault look like a ladle. Funny that a woman should think of it a ladle whereas 17th century selenographer Christiaan Huygens reckoned it looked more like a sword (ref. Modern Moon, page 147). A lightened area to the south (top of the scarp in my sketch from last night) outlined the circular ridge of Thebit S. It’s a pity it wasn’t more defined during my observation. What I found very interesting to observe was the darkened cirlce that Rupes Recta and the wrinkle ridges to the west formed. I believe the ridges to the east outline the ancient crater that Chuck Wood dubbed Ancient Thebit in the Modern Moon.
Rima Birt looked more like a thin shadow than a rille. Looking back to a sketch I rendered in 2005 using an LX200 Classic, not only was this rille visible, but I also caught Birt E, which I didn’t see during last night’s observation.
2005 rendering of Rupes Recta
Resources:
Rukl plate: 54 Birt
“The Modern Moon” by C. Wood pg. 146-147
Lunar Orbiter: Rupes Recta
PCW Memorial Observatory - Erika Rix 
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2005 05 17 – Bullialdus and Rupes Recta « PCW Memorial Observatory – Erika Rix said this on December 3, 2010 at 18:14 |