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In calibrating the cepheid scale, distances to clusters containing cepheids are found by main sequence fitting to the Pleiades. In order to optimize the main sequence fitting, it is necessary to know the difference in metallicity between the Pleiades and the cluster being fitted. As part of a study to examine these metallicity differences, we have obtained high-resolution echelle spectra of 15 of the cepheid calibrators. We are finding a spread of 0.5 dex in [Fe/H] among the cepheid calibrators. This may lead to an error of as much as 0.5 mag in derived distance modulus and hence in derived absolute magnitude. We have also obtained UBV photometry of NGC 6087 (containing S Nor) and NGC 5662 (containing V Cen) in order to go deeper down the main sequences in these clusters and obtained JK photometry of NGC 6087 to take advantage of the smaller reddening effect in K vs V-K.
We present here results of an abundance analysis of S Nor and new optical and infrared color-magnitude diagrams for NGC 6087.
