An unusually big and bright moon, often described as a supermoon, will beam down over Washington on Saturday night from a sky through which shooting stars will streak.

Astronomers say Washington area residents may be able to view both these spectacles, depending on the weather.

Clouds are in the forecast, but it was not certain how much of the sky they would obscure or for how long.

The term “supermoon” was coined to describe a moon that is both full and at its closest point to the Earth in its elliptical lunar orbit.

The combination of being full and close will make the moon seem unusually large and luminous.

At its closest approach, or perigee, the moon will be about 221,800 miles from Earth on this orbit. Perigee distances vary from month to month. The average Earth-moon distance is about 239,000 miles.

In the Washington area, the moon will rise in the east about 7:55 p.m. About three hours and 40 minutes later, it will be perfectly full and at its closest point to Earth.

Meanwhile, Earth will pass through debris from Halley’s Comet that might produce 40 to 60 meteors an hour.

In addition to any clouds, the brightness of the moon might make meteor viewing difficult. Would-be viewers were urged to keep the moon at their backs.