Skywatchers along a narrow band from west Africa to the Arabian Peninsula, India and southern China will witness on Sunday the most dramatic "ring of fire" solar eclipse to shadow the Earth in years.

Annular eclipses occur when the Moon -- passing between Earth and the Sun -- is not quite close enough to our planet to completely obscure sunlight, leaving a thin ring of the solar disc visible.

Remarkably, the eclipse on Sunday arrives on the northern hemisphere's longest day of the year -- the summer solstice -- when Earth's north pole is tilted most directly towards the Sun.

The full eclipse will be visible somewhere on Earth during just under four hours, and one of the last places to see a partially hidden Sun is Taiwan before its path heads out into the Pacific.

A solar eclipse always occurs about two weeks before or after a lunar eclipse, when the Moon moves into Earth's shadow.