Generalities: it is a zodiacal constellation of the northern hemisphere. It is of rather reduced dimensions  and  is characterized by rather weak stars. The Sun crosses it during the last decade of July and during the first decade of August. The Cancer transits at midnight in April.

Origins and mythology: this constellation belongs to the “original” ones, introduced by Tolomeus. The Cancer represents a crab that was sent by Juno to save  Hydra, the monster with seven heads that  was fighting against Hercules. The last killed the crab, which, however, as  a reward,  was set in the sky. The Egyptians identified it with a cockroach. It was once the constellation in which the Sun was found in the summer solstice .

Stars: the Cancer doesn't show any  stars under  magnitude 3; the brightest star is beta, of magnitude 3.52, of orange color. The stars gamma and delta are notable respectively, they are called Asellus Borealis and Asellus Australis. These two stars represent the two little donkeys, among which the splendid Praesepe cluster lies (M44).

Other objects: in this constellation, as already said, M44 is present, it is an open cluster called Praesepe or also Beehive, just for the great quantity of starlets that are heaped there. M44 is already visible with a  naked eye under dark skies, and it is very beautiful if observed with binoculars. The Cancer  shows also M67, another open  less fluorescent cluster.
 

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