What you would really count
Next up is the Orionids, peaking Wed, Oct 21. About 17 an hour at best from here, against a quoted rate of 20.
Every major shower
| Shower | Real rate | Why |
|---|---|---|
| Orionids Wed, Oct 21 | 17 | Radiant reaches 61 degrees. Moon score 39 that night. Debris from Halley’s Comet. A broad peak, so the nights either side are nearly as good. |
| Leonids Tue, Nov 17 | 13 | Radiant reaches 62.7 degrees. Moon score 74 that night. Quiet most years. Every 33 years or so it has produced storms of thousands an hour. |
| Geminids Mon, Dec 14 | 147 | Radiant reaches 77.7 degrees. Moon score 94 that night. The best of the year, and the radiant is high by mid evening rather than after midnight. Cold, and worth it. |
| Ursids Tue, Dec 22 | 8 | Radiant reaches 55.2 degrees. Moon score 0 that night. Small, and easy to miss beside the Geminids a week earlier. |
| Quadrantids Sun, Jan 3 | 98 | Radiant reaches 63.3 degrees. Moon score 100 that night. A very sharp peak, only a few hours wide. Miss the night and there is little left. |
| Lyrids Thu, Apr 22 | 17 | Radiant reaches 73.2 degrees. Moon score 57 that night. Modest but reliable, and the radiant is high here through the small hours. |
| Eta Aquariids Thu, May 6 | 10 | Radiant reaches 11.4 degrees. Moon score 100 that night. Strong in the southern hemisphere and poor from here: the radiant barely clears the horizon before dawn. |
| Perseids Thu, Aug 12 | 87 | Radiant reaches 60.4 degrees. Moon score 74 that night. The one everyone knows, and warm enough to sit out for. The radiant is circumpolar from here, so it never sets. |
Why the two numbers differ
The rate everyone quotes is the zenithal hourly rate. It is what one observer would count with the radiant directly overhead, under a sky dark enough to show stars at the very limit of the eye, watching the whole sky at once. Nobody has ever had those conditions. It is a laboratory figure for comparing one shower with another, not a forecast of your night.
The correction that matters most is the radiant's height. The rate you see scales with the sine of it, so a radiant halfway up the sky gives you about seventy percent, and one at 30 degrees gives you half. Below the horizon it gives you nothing at all, however famous the shower is. That is the whole story of the Eta Aquariids here: quoted at 50 an hour, and the radiant barely clears the horizon before dawn.
The moon and the light dome cut it further. Those are not folded into the figures above, because doing it properly needs a limiting magnitude and a per shower population index, and stacking estimates like that produces a confident looking number built on guesses. The moon score for each peak night is in the table instead, so it can be read for what it is.
Two things worth knowing
The Geminids beat the Perseids here. More meteors, and the radiant is high by mid evening rather than after midnight. The Perseids get the attention because August is warm and December is not.
Shower meteors are not the only ones. Five to ten an hour turn up on any dark night of the year with no shower running at all. A shower quoted at fifteen is barely above that.