Cancer - the Crab

Mythology - Queen Hera sent this crab scuttling out from a rock in the swamp where Heracles was battling the Hydra. Its purpose was to distract him and give the Hydra an edge. Sadly the plan failed when Heracles stepped on the crab and crushed it! As a reward for its valiance, Hera raised the crab into the sky.
Stars - iota cancri is a worthwhile double star to observe with binoculars and small telescopes. Its components are contrasting blue/green and yellow.
Deepsky - One of the best open clusters resides in Cancer. Præsepe or the Beehive Cluster extends twice the width of the full moon. It is visible as a large misty patch with the naked eye, but binoculars reveal some of the 300 stars that go to make it up. More challenging is M67, a smaller galactic cluster that really needs binoculars to detect it. This is a very ancient open cluster well above the plane of the galaxy.
Visibility - cancer is an early Spring constellation visible from February until April