The Ever Popular Rupes Recta

Rupes Recta

In the morning hours before sun-up the early waning crescent moon was superimposed
on the firmament just west of the Pleiades. I was somewhat transfixed by this
scene but I was set up to sketch “straight wall” on the floor of the lunar Sea of
Clouds. From the eastern edge of Mare Nubium you can see the Triplet craters
Thebit (57 km), A and L. Next moving westward is the Imbrian escarpment Rupes
Recta , not a true wall in the usual sense but on one side standing more than 300
meters high at some  points and 114 km in length. The scarp face would be visible
from crater Birt (17 km) to the west, the youngest of the larger craters sketched
here. Touching the rim of Birt to the east is Birt A.  Continuing westward we see
Rima Birt a 51 km rille from the Imbriam epoch. At the end of the rille to the
south, is tiny 3 km crater Birt F seen in this sketch. Finally sitting on a
wrinkle in the floor of the mare is crater Nicollet (15 km) a Eratosthenian epoch
impact scar.
  
  
  Sketching:
  For this sketch I used: white copy paper, graphite pencil and pen and ink 
  Contrast adjusted with Imageenhance software
  Telesccope: 18 inch f/ 5 Dobsonian working at 222X (9mm ocular)
  Date: 8-16-2006 9:30-10:35 UT
  Temperature: 17°C ( 62°F)
  Clear, calm
  Seeing:  Antoniadi  III
  Colongitude 178 °
  Lunation 22.3 days
  Illumination 45.9%
  
  Frank McCabe


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