On-sky areal coverage of our photometry (a 2 × 2 CCD mosaic covering a 44′ × 44′ region and an additional central field) in the region of the M 48 cluster is displayed with solid gray lines (green online). The dashed lines indicate the (smaller) region covered by BJG05. Stars brighter than V = 12 are marked, with symbol sizes scaled inversely with their V magnitudes. The locations of the 62 identified rotating stars (discussed later) are also indicated with circular symbols.