Canis Major is a constellation (group of stars) known as the Big Dog. In Greek myth, it is said that this constellation, along with Canis Minor, are Orion's hunting dogs. Canis Major was one of the most important constellations in ancient times because the brightest star in the sky is part of it.
Sirius, the Dog Star, is one of the brightest objects in the night sky. Only the Moon, Venus, Jupiter and Mars are brighter. People who lived near the Nile River used the star to signal the flooding of the Nile. This special occasion represented the return from the dead of the Sun god Osiris.
Canis Major is very easy to find during November through March. First locate Orion the Hunter, and imagine a straight line through his belt. Follow the line to the southeast, and you will see Sirius perched right below it. Sirius is the nose of the dog. His body stretches to the southeast, and his front leg is to the west of Sirius.
from the University of Michigan