by Marek Cichanski
After leading 100 people on a field trip all day, there's nothing quite as relaxing as coming home and spending some quality time with the Moon.
My apartment has a small "breakfast nook" patio out in back, and it makes a nice little home observing site, albeit a rather 'azimuth-limited' one. I can only see objects whose azimuth is between 180 and 240. But, when the moon's riding high as it was tonight, it transits my 'window' for a few hours of nice viewing. I set up the C5 SCT a couple of hours before sunset and observed until shortly after 10 pm.
The seeing started out average to slightly below average, but got better as the night wore on. It got particularly good shortly before the marine layer started to form up, at about 10. Something like this happened last night at Hogue, too. Maybe the onset of a marine layer is accompanied by a particularly laminar flow?
With the sun still up, I started by identifying large and/or prominent features using Rukl's "The moon at first quarter" full-disk photos. A 25mm Orion Plossl was used. (All compass directions are in the astronautical convention, and times are UT, whose date was 6/8.)
Maria: eastern Frigoris, eastern Imbrium, Serenitatis, Tranquillitatis, Fecunditatis, Crisium, Nectaris, Sinus Asperitatis. E limb of moon is tipped away from earth, so no Marginis or Smythii, but some (most?) of Australe is visible. Lacus Spei (the Lake of Hope) is just barely visible. Lacus Somniorum and Lacus Mortis can be seen connecting Serenitatis to Frigoris.
Major craters: Aristoteles, Eudoxus, Aristillus, Autolycus, Archimedes, Bessel, Plinius, Agrippa, Godin, Triesnecker, Albategnius, Ptolemaeus, Alphonsus, Arzachel, Herschel, Purbach, Walter, Werner, Aliacensis, Maginus, Proclus.
Other features seen at this scale were the Palus Somnii, formed by the asymmetrical ray pattern of the crater Proclus, Vallis Alpes, a tectonic cleft (a.k.a. a 'graben') cutting across the lunar Alps, and the Rupes Altai, a great arcuate east-facing cliff, one of the shock rings of Mare Nectaris.
Switching to a bit more magnification - the 16mm Nagler type 6:
The floor of Ptolemaeus looks perfectly smooth, except for the craterlet Ammonius. The floor of Alphonsus is slightly less smooth, and has a central peak. Was Ptolemaeus flooded by lava, with the central peak being buried? Why not Alphonsus? What does this imply about the fracture system that provided the "plumbing" for the lava's ascent, vis-a-vis the interconnectedness (or lack thereof) of this fracture system?
Arzachel: A classic, terraced-walled, central-peaked crater.
Floor of Maginus is partly lit. Craterlets visible on floor. W wall is heavily superimposed by craters.
Floor of Moretus was completely in shadow earlier, but now the central peak is BARELY beginning to get lit. (1:04 UT)
Craters Orontius - Huggins - Nasireddin: A wonderful progression of ages! Each crater overlaps the one to its east. Bing, bang, boom. Can't tell the relative ages of Nasireddin and Miller to its north - the two craters are perfectly tangent to each other.
Cool! Rupes Recta (the Straight Wall, a west-facing fault scarp) is JUST beginning to appear, casting a long shadow.
Floor of crater Plato, at N rim of Mare Imbrium, is fully shaded. (3:46 UT).
Now, for the rest of the evening, I'll kick the magnification up even a bit more, with the 9mm Nagler type 6. (I used the 4.8mm original Nagler for a few closer looks.)
Rukl 22 (Palus Putredinis area, famous for being the home of the Apollo 15 site):
Mons Bradley and Mons Hadley casting prominent shadows onto the mare to the west.
Rima Bradley showing up well. It transects hummocky material NW of the Appenines. (Is this the Appenine Bench Formation? What is this material - Archimedes ejecta?)
Montes Archimedes are looking prominent and lumpy.
Montes Ampere and Huygens look like colossal projecting spurs, like portions of the walls of Yosemite Valley. Makes it look like the N buttresses of the peaks are quite steep.
Not quite seeing Rima Hadley (of Apollo 15 fame) in this seeing. (No joy with the 4.8mm either.)
Rukl 54: (Ah yes, the famous Birt...)
Rupes Recta is casting a very sharp, dark shadow. It looks like a very steep scarp (but isn't really very steep, according to Rukl.)
Craters Birt and Birt A appear to be quite tall-walled, due to the shallow angle of illumination. No joy on Rima Birt in this light and seeing.
Rukl 55 (Arzachel):
Rimae Arzachel just BARELY visible; has just barely cleared the rim shadow.
Various other things observed:
Seeing is starting to get pretty good (4:41 UT). Can now see bits of Rima Hadley in moments of good seeing.
Can tell that the floor of Vallis Alpes is irregular, but can't see the rille distinctly. Cassini and its craterlets now well-seen. Mons Piton: "Magnificent isolation". Montes Spitzbergen: In the SCT view, it looks like a map of the Philippines. Mons Pico: Shadow connected to terminator. The shadow of M.P. beta is almost, but not quite connected to the term. The W half of the floor of Plato is lit, with long shadows. In Ptolemaeus: It looks like there's a flooded, "ghost" crater tangent to Ammonius on the north.
Tried for Catena Davy, before the moon was obscured by clouds and the edge of the building, but no joy. (5:05 UT)
A fun, relaxing night. A great way to unwind after a busy day.