BETTER DISTANCES TO OPEN CLUSTERS THROUGH CALIBRATED ISOCHRONES

We present a progress report on our efforts to improve the calibration of theoretical isochrones using nearby stars and clusters with accurate parallaxes. Previously, we confirmed that several widely-used color-temperature relations have significant systematic errors, and proposed an adjusted color-temperature relation in BV ICKs based on the Hyades. Here, we show that these calibrated isochrones give internally consistent distances to nearby open clusters at the metal abundances indicated from high-resolution spectra. Finally, we present new time-series photometry of spotted variable stars to explore the causes of the significant departures from the isochrone lower main-sequence seen in the photometry of young open clusters.