Object name: M103
M103 is a somewhat young cluster being about 22 million years old according to WEBDA. Other sources say it to be 25 million years old. When a cluster forms it is made up of a few super hot short lived stars and far more dimmer sun type stars and even more faint red stars. The huge super hot stars die quickly. Many won't even make it to 20 million years of age. So by studying the color of the stars in a cluster, we can tell its age. It can't be any older than the maximum age of its hottest, bluest stars. Since they are very bright, even though few in number they provide nearly all the light of a young cluster. In the case of M103, located at the edge of the Milky Way in Cassiopeia the fainter members are very difficult to tell from background Milky Way stars. This cluster is at a distance of 7150 to 9200 light years, distant for an open cluster. So even in my scope, the typical star is too faint to see as a cluster member.