The name given by Arabic astrologers to a certain dim star that hides behind a brighter companion (unlike, say, the vice-president of the U.S., who hides behind a dimmer luminary). Who can see Alcor with the naked eye is said to have keen vision. It is worth remembering that this same distinction was said to apply to the raiment of a well-known emperor.

ALCOR - ALgol COnverteR