RING OF SOLAR FIRE
Total eclipses are rare, but partial eclipses occur more frequently. While enjoyable to view with the right equipment, partial eclipses lack the overwhelming drama of a total eclipse and few people will travel very far to see one.
A possible exception is the annular eclipse, a special type of partial eclipse. Annular eclipses happen because the
Moon's orbit around Earth— and Earth's orbit around the
Sun—are not circular but elliptical. Thus the apparent sizes of the Sun and Moon vary by a small amount. On occasion, the Moon may appear too small (or the Sun too large) for a total eclipse to occur, even though other circumstances are right for it.
The result is that at maximum eclipse the Moon does not cover the Sun completely, and a ring (or annulus) of the Sun's uneclipsed surface surrounds the black circle of the Moon. Annular eclipses will not show you the Sun's corona (unless the eclipse is about 99.99 percent total), but they can be quite spectacular all the same, especially if the Sun is sitting near the horizon.