Skywatchers in East Asia and the western United States should circle this upcoming Sunday on their calendars. That's when a solar eclipse will block out most of the sun, leaving a spectacular "ring of fire" shining in the sky for observers located along the eclipse's path.

The event is what's known as an annular solar eclipse — from the Latin "annulus," meaning "little ring" — and its full glory should be visible from much of Asia, the Pacific region and some of western North America, weather permitting. At its peak, the eclipse will block about 94 percent of the sun's light...