Starry nights are a limited ressource up here in N. temperate Europe, and so I've not had the chance to spend as much time on the moon, as I'd like to. I did however manage to do an overview study of my favourite region on the moon: the Aristarchus Plateau, and so here's my report from that night in late January this year (2016).
Procellarum NW, 11 dy
It’s late January 2016, 22h local time. There’s a 11 day waxing gibbous (83% illum.) moon hanging high up (ca. 50° alt.) almost due south, on the border between Orion and Gemini. The weather is calm and freezing (-10°C/14°F) with above medium transparency and seeing, and after 20 minutes under the stars my Vixen FL-80S doublet refractor has now fully adapted to the >25°C temperature drop from the warm room inside our house. There’s is no wind, and so it doesn’t feel too cold to make a drawing, but my breath is condensing and freezing on the eyepiece turret, so I have to breathe gently out the corner of my mouth…
I point my small refractor at the Moon, centering the view at Aristarchus and the surrounding plateau in the NW part of the great Procellarum Basin. This is one of the most geologically diverse areas on the near side of the Moon, with records of lunar history from the ancient pre-Imbrian (>3.8 BY) up to the youngest Copernican epoch (<1 BY).
The Imbrium basin impact (3.9 BY) threw up a 4km thick layer of ejecta on top of the surrounding rims and caused a series of linear (radial as well as concentric) tectonic segmentations and faults, including the subsequent 2km uprising of the 170x200 km, diamond-shaped Aristarchus Plateau. The following Orientale basin impact plus the large Herodotus and Prinz craters (all lower Imbrium: ~3.8 BY) further coated the plateau with primary ejecta and secondary craters (thus reseting the crater-age clock of the plateau).
The oldest mare lava extrusions (3.6 BY upper Imbrian red Teleman lava) is found along the extensive faults at the plateaus NW (“Agricola Straits”) and E borders; This early flooding was accompanied by pyroclastic vulcanic eruptions, that coated the plateau and surroundings with a 10-20m deep red iron-rich glassy fine-grained ash : Dark Mantle Deposit (DMD).
Later highly fluid lava (2.7 BY old Eratosthenian dark blue Sharp lava) was erupted from many rimless cobra-head vents, from which they eroded narrow channels down-gradient, including the largest sinuous rille on the Moon, Schröter’s Valley on the plateu (11 km wide and almost ½ km deep, running downslope 160 km to the NE). The erupted lava flooded the Plateau surroundings including the floors of the afore mentioned large impact craters (Herodotus and Prinz).
Aristarchus is a very young (175 MY), 42km wide and 3km deep impact crater from the Copernican epoch (<1 BY); It is sharply defined with a well-developed terassed inner wall, very bright with a high reflectivity caused by underlying anorthositic highland rocks, that has been excavated by the deep impact (Aristarchus is easily spotted in in my 8x30 bino).
There are a lot of smaller geologic features visible under favourable conditions, and with larger telescopes : the dark bands in the western crater wall of Aristarchus, the small cobra head vents and rilles in the Montes Harbinger region, the sinous rilles Rimae Aristarchus to the NW of the plateau, the steep mare ridge edge Rupes Toscanelli, the lunar dome Herodotus Omega just S of Herodotus, the Dorsum Niggli running from the Mts. Agricola across the Agricola Straits to the Aristarchus Plateau, the bright ejecta rays from crater Aristarchus, and much more.
I consider this an overview study of the area, and am looking much forward to future detail studies with my small refractors.
Here's a ->link to the OBS. Report<-, with more details.
Edited by AllanDystrup, 07 April 2016 - 04:16 AM.