A loose, irregular cluster of galaxies some 500 million l.y. away in the constellation Hercules; also known as Abell 2151. The cluster is 1°.7 wide as seen from Earth, has a true diameter of 6 million l.y., is flattened in shape, and is notable for the high proportion of spirals among its bright members. There are about 75 bright galaxies, and many fainter members.