Summer's best low-tech sky event — the Perseid meteor shower — will be a wash-out this year with moonlight set to spoil the show.

A full moon will shine all night tonight into Saturday, the peak of the Perseids.

The pre-dawn hours are usually when the Perseids are the most numerous. That's also when the constellation Perseus — from which the meteors appear to radiate — is the highest in the northeast sky.

The constellation, named for Greek hero Perseus, lies beneath the constellation Cassiopeia, which many people recognize as a big "W" of five fairly bright stars.

The Perseids, which are bright, fast and sometimes can flare into fireballs, can number as high as 100 per hour when the moon doesn't get in the way. Experts say this year may reap 20-30 per hour.

The meteor shower is the result of Earth moving through debris left by the passage of the Comet Swift-Tuttle in its 130-year orbit of the sun.

Travelling at about 36,000 miles per hour, the rocky debris ranges from the size of sand to peas. When they strike Earth's atmosphere up to 80 miles high, the friction causes them to flare as they disintegrate.

For the best viewing, get away from city lights to a dark spot and allow your eyes to adjust for about 20 minutes. Then look to the north although the meteors may appear anywhere in the sky.