04/02/17. First Quarter Ascending Moon, 17:00 - 19:00 (Transit 18:40) GMT, 56.4% illumination, azimuth 334.6°, altitude 48.2°, 369,932 km distant (Pisces). Conditions ranged from quite clear to hazy thin cloud to clear again and eventually degenerating into fairly heavy cloud. Telescope: 90mm Orion Apex, alt az mount. Baader Neodymium filter in (Amici prism) diagonal. Magnifications of 50x, 66x, 83x, 89x, 100x, 125x and 156x. I started at 50x as it was technically still daylight and that’s good enough to check overall transparency. Detail was good though and as it got progressively darker I increased the magnification to 83x and then 89x. Occasionally I would have to drop back down to 83x or even 66x. After transit there was a prolonged period at 100x and 125x. For a short while I even managed a clear, bright 156x but eventually conditions deteriorated again.
Highlights include superb terminator detail in the Caucasus and Apennine mountain ranges, Conon was very easily discerned, Ptolemaeus, Alphonsus and Arzachel were clear with much internal detail. Arzachel’s central mountain was very apparent as were its walled terraces. Albategnius was quite striking with the steep slopes of Klein dramatically shadowed. Deslandres, Hell and Lexell were all quite prominent and I even got a hint of Clavius and Rutherfurd further south.
An interesting surprise was just how contrasted the Pallas crater and general area north and west of the Sinus Medii were. I almost imagined I could perceive 'Wallwerk’ the lunar city Baron Franz von Gruithuisen believed he could see in the 19th century. When the terminator catches some of the area just right it does indeed give the impression of walled cities or ancient ruins.
Images by courtesy of the Virtual Moon Atlas