They knew this back then?!
"An eclipse of the moon occurred on 31 July. Having mentioned this event, it is as well to describe, for the uninformed, the nature of an eclipse. It is a failing or deficiency of the moon. An eclipse of the moon occurs as often as it falls under the shadow of the earth; for it (the moon) is said to have no light of its own, but is thought to be illuminated by the sun."
from Byrthferth's Northumbrian Chronicle, section IV: the Northern Annals, 752.
from Byrthferth's Northumbrian Chronicle, section IV: the Northern Annals, 752.