Accurate Stellar Population Studies from Multiband Photometric Observations

We present a new technique based on multi-band near ultraviolet and opticalphotometry to measure both the stellar intrinsic properties, ie luminosity andeffective temperature, and the interstellar dust extinction along the line ofsight to hundreds of stars per square arcminute. The yield is twofold. On theone hand, the resulting reddening map has a very high spatial resolution, ofthe order of a few arcseconds, and can be quite effectively used in regionswhere the interstellar material is patchy, thus producing considerabledifferential extinction on small angular scales. On the other hand, combiningthe photometric information over a wide baseline in wavelength provides anaccurate determination of temperature and luminosity for thousands of stars. Asa test case, we present the results for the region around Supernova 1987A inthe Large Magellanic Cloud imaged with the WFPC2 on board the Hubble SpaceTelescope.