Ursa Major, the Great Bear, is visible in the Northern Hemisphere all year long. It contains the Big Dipper and is the best known of all the constellations, appearing in every reference known.
Callisto was changed to a bear, because of Zeus's jealousy, and transferred to the sky. This is improbable, as the constellation was already well established before this time. The drawings all show a bear with a long tail, which is again not likely correct since bears have no tails.
