In various parts of the heavens stars are seen crowded together, forming what are called star clusters. Several of these objects can be distinctly seen with the unaided eye, but the greater number require the telescope to render them visible. The most conspicuous of the naked-eye groups, the well-known Pleaides, is situated in the constellation of Taurus. In this cluster, with ordinary eyesight only, six or seven stars can be seen, but with the telescope the number increases with the space-penetrating power, and with some instruments over 400 stars can be counted.
