As the sun sets in the west Saturday, the biggest, brightest moon in about 20 years will begin peeking over the eastern horizon.
The so-called "supermoon" will appear about 14% bigger and 30% brighter than normal, according to NASA.
Because the moon's orbit is oval, there is a point where it is the closest to the Earth, known as its perigee. The farthest point is its apogee.
On Saturday, the moon's closest perigee of the year happens to occur within one hour of the monthly astronomical phase of the full moon, which together will create the rarely seen spectacle of illumination and size, said Geoff Chester, an astronomer at the U.S. Naval Observatory in Washington.
"It will be the closest full moon we've had since 1993," he said. Those who hope to maximize their viewing experience should set their sights on the distant horizon with objects such as mountains or buildings in the foreground, which will make the moon appear even larger, Chester said.