Resolving Extragalactic Star Clusters with HST/ACS

With HST, colour-magnitude diagrams (CMDs) can be obtained for young star clusters well beyond the Local Group. Such data can help constrain cluster ages and metallicities, and also provide a reference against which intermediate- and high mass stellar models can be compared. Here, CMDs are presented for two massive (>10^5 Msun) clusters and compared with Padua and Geneva isochrones. The problem of the ratio of blue to red supergiants is also addressed.