Solar eclipse. Computer artwork of the diamond ring effect of a total solar eclipse (centre left) seen above the astronomical telescope domes (lower centre) at Mauna Kea, Hawaii, USA. The diamond ring effect, observed at the beginning and end of a total solar eclipse, is caused by the first and last glimpse of the Sun shining through valleys on the limb of the Moon. A solar eclipse is caused by the alignment of the Moon between the Earth and the Sun, blocking out the Sun's light from regions on Earth that lie in the Moon's shadow. A total eclipse, as seen here, is possible because the diameters of the Sun and Moon appear similar from Earth.