A Lunar Interlude

22 March, 18:30 – 20:00 

Technically not a deep-sky post, but with the Moon just past first quarter and about as high in the sky as it can get, there's no better time to observe our nearest neighbour. Highlights included the familiar Straight Wall plus the nearby Rima Birt. Another rille was visible inside the rim of the crater Pitatus, as well as a section of the Hesiodus rille (showing a distinctly flat floor). The full extent of the Hadley rille was visible (always an indicator of good seeing) – enabling me to pinpoint the Apollo 15 landing site. Lots of fine detail in and around the Fra Mauro region. Copernicus looming on the terminator (rim illuminated, interior shadowed) with super-fine detail in the surrounding ejecta pattern. This was one of those rare occasions where I used all five Tele Vue eyepieces, although the seeing wasn’t quite good enough to warrant going above 240x with the Powermate.

I also tried Sirius again (this time in deepening twilight, after seeing a tip on Cloudy Nights), but there was still no sign of the Pup. I think the main problem I have is that when Sirius is at its highest altitude from my location, the diffraction spikes from the secondary mirror are always going to obstruct the view of Sirius B.

Nature note:

The dunnock was singing sporadically again, but the most notable observation of the evening was the sheer number of birds seen silhouetted against the moon: waves and waves of them, mostly flying east – and at a very high altitude. The sky was still somewhat blue when I first noticed them through the eyepiece, but they were invisible to the naked eye. It was very difficult to tell exactly what they were, but I would guess they were winter thrushes (fieldfares, redwings) returning to their breeding grounds.

23 March, 19:00 – 20:00

The seeing was even better tonight (although it tailed off steadily once the Moon crossed the meridian). Observations carried out at 171x (DeLite 7mm), 333x (Nagler 9mm + 2.5x Powermate) and 428x (DeLite 7mm + 2.5x Powermate).

Highlights: The three largest Plato craterlets were resolved as actual craters, as opposed to white spots. I couldn’t see the rille in Vallis Alpes, though after reading up on it later I realised I’d underestimated just how narrow it is relative to the valley. Wealth of detail in and around Copernicus – easily the best view I’ve ever had of it. Wrinkle ridges in Mare Imbrium. Cape Laplace (on the edge of Sinus Iridum) casting a very long shadow.

Moving south to Mare Nubium: The rest of the Hesiodus rille was now visible. The concentric crater structure of Hesiodus A was showing very well. Dome visible in Capuanus crater. Ramsden rilles showing really well (reminiscent of the Triesnecker complex). Hippalus rilles (from Mare Humorum) near the terminator.

Also worthy of mention: A very bright ISS pass at 19:30, moving high over the Moon and almost touching Pollux in Gemini. While this was going on I also noticed an extremely bright flare in the east from another object which looked to be travelling on a similar orbit to the ISS, roughly 90 degrees ahead of it. I haven’t yet been able to determine what it was. Stellarium plots several satellites passing through that area around that time (including a few of the ubiquitous Starlinks), but none of them appear to be related to the ISS.

Nature note: 

Still a few birds flying across the face of the Moon, but not nearly as many as the previous evening.