A total lunar eclipse, as seen on May 20, 2003 . Lunar eclipses, far more common and visible over a much wider area than solar eclipses, occur when the earth's orbit takes it between the sun and the moon, casting the latter into shadow. Even during totality the moon remains illuminated by light refracted around the limb of the earth. The reddish glow is a result of the tendency of the earth's atmosphere to scatter blue light more than red. (hence our blue sky).