A lunar sketchbook
Everything interesting happens along the line between light and dark. Two nights either side and the same crater is a flat grey ring with nothing to say.
Colongitude is the number worth planning around. It says where the sunrise line falls far more precisely than the phase does, and repeats closely enough that a feature caught at 31° one month can be found again at 31° the next.
The arc of craterlets across the floor is the whole reason to come back to this one. They emerge in order as the light creeps in — the largest first, then four more stepping down in size along the curve, and the smallest only on a night when the air is genuinely still.
Got five on this attempt. The sixth is supposed to be there and I have never convincingly seen it.
The Straight Wall, which is neither straight nor a wall — a gentle fault scarp that looks like a knife cut for about two nights a month and is invisible the rest of the time. Casts a dark line near first quarter and a bright one near last.
Easier to draw than most things on the Moon and satisfying out of all proportion to the effort.
A flat dark disc with almost nothing in it, which is exactly the challenge — the floor craterlets are tiny and sit right at the limit. The value of drawing it is that the pencil forces you to look for twenty minutes instead of two.
Four spots recorded, two of them with no confidence at all, marked as such on the sheet.
Graphite on grey paper with a white pencil for the highlights, which is far quicker than working light-on-white and closer to how the thing actually looks at the eyepiece. Twenty to forty minutes a sketch, done at the telescope and never tidied up afterwards.
Anything uncertain gets marked on the sheet at the time. A drawing that quietly includes features the observer did not really see is worse than no drawing at all.