Abstract

Open clusters, such as the Pleiades, Praesepe, the Hyades, and NGC 6811, are critical benchmarks for calibrating stellar properties such as rotation and magnetic activity. I will discuss recent rotation measurements in open clusters, including the first periods measured for fully convective Hyads. Discrepancies between open cluster data and models of angular momentum evolution imply that we still do not fully understand how magnetic fields affect stellar spin-down. I will show how we can use these clusters to test theories of stellar magnetic fields. Finally, I will discuss the potential impact of binary companions and protoplanetary disks on stellar angular momentum evolution.