The Baily's beads effect, or Diamond ring effect, is a feature of total and annular solar eclipses. As the moon goes by the Sun during a solar eclipse, the lunar limb topography allows beads of sunlight to shine through in some places, and not in others. The effect is caused due to the rugged lunar surface. The diamond ring effect is seen when only one bead is left, a shining diamond set in a bright ring around the lunar silhouette.
Lunar topography has considerable relief because of the presence of mountains, craters, valleys and other topographical features. It is not safe to view Baily's beads or the diamond ring effect without proper eye protection because in both cases the photosphere is still visible.
In the path of totality at a solar eclipse can see first a gradual covering of the Sun by the lunar silhouette for over an hour, and then a set of Baily’s beads. As the Baily’s beads disappear behind the advancing lunar edge a thin reddish edge, called the chromosphere appears. Though the reddish hydrogen radiation is most visible to the unaided eye, the chromosphere also radiates thousands of additional spectral lines.