by Matt Tarlach
Well, the sun still hasn't risen on Wargentin, and the Sandman's gotten the better of me. I did get some nice views of Schickard near the terminator, but spent most of my time tonight in the Aristarchus region, on Rukl's chart 18. Seeing was seldom better than 2/5, and I did most of the observing with 130x on the 80mm Vixen refractor.
With a little better seeing, and a higher Sun, I have a different take on Schroter's Valley than reported in my last post. The domelike feature at the southern end of the Cobra Head was more evident his time. Now I think the Cobra Head itself, and next 20km or so of the valley, may be the collapsed remains of a northern extension of this dome. If they began as an elevated structure, which subsequently collapsed, it would explain the ridged walls of the valley that I traced up past 25.5* north. Under tonight's seeing, at least, I was unable to see ridged walls any further north along the rille.
Mons Herodotus had an odd appearance, right near the terminator at 0730 UT. Bright white against the dark mare/lava surroundings, it appeared as the central pinnacle of a very large, dark, domelike structure, triangular in shape, perhaps equilateral allowing for perspective, with the eastern side running pretty close to N-S. The dorsum-like structure plotted by Rukl to the east of Mons Herodotus approximates this eastern rampart.
Right on the terminator, the Montes Agricola and southern wing of the Dorsa Burnet seemed to form a continuous arc. The appearance suggested the remains of a huge ruined ring under this extreme lighting.
The Rupes Toscanelli was a soft-looking black mark, like somebody drew on the Moon with a giant Sharpie.
The Marius Hills were much in evidence, between their namesake crater and the terminator. The domelike hills in this area appear taller and steeper than the very low, soft-looking domes near Copernicus. Perhaps it's a trick of perspective, these being seen more obliquely, rather than from nearly above as with those in the Copernicus region.
Speaking of domes and volcanic features, last night (6/13 UT) I got a good look at the Gruithuisen mountains. Seeing was better, and for a moment at 180x I thought I could see the crater pit Rukl plots atop Gamma. But no, the dark area I glimpsed was too far north; perhaps I detected the curve in the northwestern slope of the mountain. Summit crater or no, these mountains strike me as some of the most obviously volcanic features on the Moon. Their soft, curved appearance contrasts with the broken, impact-cratered surface to the northwest, and reminds me strongly of terrestrial volcanic cones.