The recognition of unusual objects in the Sloan Digital Sky Survey color system

We present five-filter photometry of 21 carbon stars; 15 asteroids; 15 cata clysmic variables; six metal-poor stars; five Cepheids; 1775 field stars, b lue horizontal-branch (BHB) stars, and RR Lyrae stars in the globular clust ers M15 and M2; two primary standards; and 19 secondary standards. The phot ometry was carried out using a filter set identical to that which will be u sed for the Sloan Digital Sky Survey. We find that carbon stars, CVs, R-typ e, J-type, and V-type asteroids, BHB stars, and RR Lyr stars should be iden tifiable on the basis of Sloan Digital Sky Survey photometry alone, whereas Cepheids, metal-poor stars, and many types of asteroids are indistinguisha ble from the stellar locus of field stars.