The RR Lyrae variables in M54 and the Sgr dwarf galaxy

We report on new B, V and I CCD photometry of the globular cluster M54 that was aimed at the study of its variable stars. With respect to the previous most recent work on M54 we have nearly doubled the number of detected variable stars: M54 can now be classified as intermediate in the Oosterhoff groups. The metallicity distribution for the cluster and the Sgr dSph field is obtained from the red giant stellar population, and for the variables.