The moon that rises over Washington on Saturday night will be what has come to be called a “supermoon” — only hours from being perfectly full and hours from one of the year’s closest approaches to Earth.

The combination makes for a moon that appears bigger and brighter than usual, even for a full moon. In addition, because the moon always looks larger as it rises, moonrise Saturday night may show off a moon that appears about as big, bright and round as the moon can get.

The moon will rise in the southeast at 8:36 p.m. Saturday. The silvery orb will sail west across the dark heavens through the night and early morning before setting in the southwest at 7:20 a.m. Sunday.

Experts warn that without special equipment it may be difficult for the average skywatcher to assess the moon’s brightness or size. But a supermoon last year was reported to be about 15 percent larger and 30 percent brighter than the year’s run-of-the-mill full moons, and many people may consider themselves capable of spotting a 30 percent boost in brightness.

Of course, the brightness of the moon, as seen from earth, will depend, in part, on the sky’s clarity and the amount of cloud cover. If clouds do intervene, the next supermoon is not far off. There will be one in August and another in September.