A first-quarter Moon at 70×, with a drawing I am not proud of
People who own telescopes are slightly embarrassed about the Moon. It is too easy. It is bright enough to see from a town centre, it washes out everything faint for a week either side of full, and it is the first thing a new telescope gets pointed at and the first thing the owner stops looking at once they discover galaxies. I went through that phase too, and I was wrong. Through a 70 mm refractor the Moon is the only object that fills the eyepiece with more detail than I can take in, and it does that every month.
The trick, which every book says and which I ignored for an embarrassingly long time, is to avoid the full Moon. At full, sunlight falls straight down on the surface and there are no shadows. Everything is flat and white and glaring. Around first quarter, the line between day and night (the terminator) runs down the middle of the disc, the Sun is rising over that part of the Moon, and every crater and ridge near the line casts a long black shadow. Relief appears out of nowhere.
Yesterday was first quarter. The sky cleared at about nine, and the Moon was high in the south-west, well above the roof of the house opposite, which is my usual obstacle.
The log
- 21:10 Telescope out on the garden table, left to cool. A small refractor does not need long, but the eyepieces were in a warm drawer and I wanted them to stop fogging.
- 21:25 First look at 28×. The whole disc fits with room to spare. The terminator is very slightly past the middle, so the Moon is a fraction more than half lit. Mare Crisium, the isolated dark oval near the eastern edge, is the easiest landmark. Then Tranquillitatis and Serenitatis, the two large grey plains running towards the middle.
- 21:35 Up to 70×. Seeing reasonable: the image shimmers, but every few seconds it locks still and the detail jumps out.
- 21:40 Following the terminator south from Tranquillitatis. Three large craters in a chain: Theophilus, Cyrillus and Catharina. Theophilus is the sharpest of the three, with steep terraced walls and a central mountain group that is catching the light while the floor around it is still in shadow. Cyrillus beside it looks older and more worn, and Catharina, the southernmost, is battered almost into a ring of hills. I had read that they are a lesson in age, the youngest overlapping the older, and it is genuinely visible: Theophilus cuts into Cyrillus's rim.
- 21:55 Curving away to the south-west of the chain, a long bright line: the Altai scarp, a cliff hundreds of kilometres long, lit side-on. At 70× it looks like a crease in paper.
- 22:05 North, to the lunar Apennines, a range on the edge of Mare Imbrium, which was just coming into sunlight. Peaks were standing out as bright points beyond the terminator, in the dark, because their summits catch sunrise before the ground below them does. This is my favourite thing on the Moon, and I had not seen it before because I had never looked at the right day.
- 22:15 Near the Apennines: three craters close together, Archimedes, Aristillus and Autolycus. Archimedes has a flat dark floor, the other two are smaller and brighter. To the north, faintly, the Alpine Valley, a straight slot through the mountains at the top of Imbrium. I saw it with averted vision more than directly, which seems absurd for something on the Moon, but it is narrow and the contrast was low.
- 22:25 Started the drawing. See below.
- 22:45 Pencil down, hands cold, Moon sinking into the haze above the roofs.
What I did not see: the Straight Wall, which I had hoped for. It needs the terminator a little further west, which means another day or so. Plato, the dark flat crater at the northern edge of Imbrium, was still on the night side.
The drawing
I drew Theophilus and its neighbours rather than the Apennines, because craters are easier to draw than mountains and I was cold enough to want the easy option. Soft pencil on cheap cartridge paper, a red torch clipped to the table, about twenty minutes.
It is not a good drawing. Theophilus is too round and Catharina looks like a dropped doughnut. But making it changed what I saw. I had been looking at the chain for half an hour before I picked up the pencil, and only while drawing did I notice that the central peaks of Theophilus have more than one summit, that the shadow on its floor has a jagged edge where the wall is terraced, and that there is a small sharp crater on the flank of Cyrillus I had not registered at all. Drawing makes you decide where things go, and you cannot decide without looking again.
There is a long tradition of lunar observers drawing rather than photographing. Photographs record the light; drawings record the attention. I understand that now in a way I did not when I first read it.
For next month
- Go out a night later as well, for the Straight Wall and the sunrise over Plato.
- Keep the eyepieces in a coat pocket rather than a warm drawer.
- Do not try to draw a whole region. One crater, properly, is plenty.
- Bring something to eat. I did not, and the half-Moon looked increasingly like a slice of bread.
A note on the light. A half Moon is bright, and after ninety minutes at the eyepiece my observing eye took a while to see anything else. I tried for the Beehive cluster, which should be an easy binocular object at this time of year, and could barely find it. Moon nights are Moon nights. Everything else can wait for the dark half of the month.