What are our observational tests of Stellar Evolution? This lecture

discusses how we use Hertzsprung-Russell Diagrams of star clusters

to test stellar evolution theory, and some of the conclusions we have

drawn. In particular, we will see how the age of a star cluster can

be estimated from the Main-Sequence Turn-Off for the cluster. We

also introduce Open and Globular Clusters, and show how we apply

stellar evolution theory to their H-R diagrams.

Recorded 2006 February 2 in 1008 Evans Laboratory on the Columbus campus

of The Ohio State University.