Perseids 2025, and the Moon that ruined them
I knew this year's Perseids would be poor before I went out, and I went out anyway, which is the usual relationship between amateur astronomers and meteor showers. The peak fell on the night of the twelfth into the thirteenth. Full Moon had been on the ninth. That left a waning gibbous Moon, still more than four-fifths lit, rising mid-evening and climbing through the hours when the radiant in Perseus was getting high enough to matter. Moonlight drowns faint meteors, and most meteors are faint.
NASA's monthly sky guide for August says as much, politely. This JPL "What's Up" episode is about three and a half minutes long and is worth watching for the Perseids section, which is frank about the Moon:
The log, 12–13 August
| Time | Meteors | Notes |
|---|---|---|
| 21:45–22:30 | 2 | Sky still deep blue in the north-west. Both were long, slow earthgrazers from low in the north-east. |
| 22:30–23:15 | 1 | Moon up behind the houses to the east, sky brightening visibly. |
| 23:15–00:00 | 2 | Moon clear of the roofs. Limiting magnitude perhaps 4 at the zenith, worse elsewhere. |
| 00:00–00:30 | 2 | One genuinely bright, a short orange streak through Cassiopeia. Gave up at half past. |
Seven Perseids in two and three-quarter hours. Last year, from the same chair, I counted about three times as many in the same time, and that was with the street lamp. I spent most of the evening with my back to the Moon and my hand up against the lamp, which is an observing posture I have come to think of as the suburban salute.
The early meteors were the best ones. When the radiant is low, the few Perseids you see skim through the upper atmosphere at a shallow angle and leave long, slow trails across half the sky. They are rare but they are worth the early start, and they happened before the Moon was a problem.
Dawn
I had read that Venus and Jupiter would be close together before dawn, so I set an alarm for 04:30 and went back out in a coat over pyjamas. Low in the east-north-east, in the brightening twilight, Venus and Jupiter were very close together, about a degree apart, near enough that both fitted easily in the field of the 10×50 binoculars with plenty of room to spare. Venus was the brighter by far, a hard white point; Jupiter a softer cream. For a minute or two I thought I could hold one of Jupiter's moons beside it, a tiny point on the edge of seeing, before the sky got too bright to be sure.
I saw one more Perseid at 04:50, a short one straight down through the moonlit sky. That makes eight. I am counting it.
For next year
Check the Moon first. I know this. I knew it this year too. The shower is the same every August, but the Moon moves about eleven days earlier in its cycle each year, so a bad year is often followed by a much better one. If the forecast is clear and the Moon cooperates, it may be worth the drive out to a darker field rather than the back step. That decision can wait for the summer.
On the way back to bed I took the last of the Mischbrot out of the bread bin and ate a slice standing up in the kitchen. Moonlight through the window, eight meteors in the notebook, rye at five in the morning. Not a great Perseids, but not a bad night.