The number of meteors one observer would see in an hour under a perfect sky (limiting magnitude 6.5), with the radiant at the zenith. It is a theoretical maximum: in practice you often see two or three times fewer. For the Perseids it is about 100.
Related terms
- Meteor shower
When the Earth passes through the dust trail left by a comet, meteors multiply for a few nights. The Perseids peak around 12 August and the Geminids around 14 December, with up to 100 to 150 meteors an hour in ideal conditions. Watch them with the naked eye, lying down, away from lights.
- Radiant
The point in the sky from which the meteors of a shower seem to stream, a perspective effect like railway lines meeting in the distance. It gives the shower its name: the Perseid radiant is in Perseus. The higher it is, the more meteors you see; no need to stare at it, though.
- Limiting magnitude
The brightness of the faintest stars you can see. With the naked eye it ranges from 3 or 4 in a city to 6.5 or more under a very dark sky. A telescope of aperture D (in mm) pushes it further by about 5 log₁₀(D ÷ 7) magnitudes: a 200 mm telescope reaches roughly magnitude 14.
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