In this catalog , Shapley could see most of the ` Coma-Virgo cloud ' ( now known to be a superposition of the Coma Supercluster and the Virgo Supercluster ) , but found a ` cloud ' in the constellation of Centaurus to be the most striking concentration of galaxies .
He found a ` cloud ' in the constellation of Centaurus to be the most striking concentration of galaxies .