  The light variations of first-overtone RR Lyrae stars and contact eclipsing
binaries can be difficult to distinguish. The Catalina Periodic Variable Star
catalog contains several misclassified objects, despite the classification
efforts by Drake et al. (2014). They used metallicity and surface gravity
derived from spectroscopic data (from the SDSS database) to rule out binaries.
Our aim is to further constrain the catalog using SDSS colours to estimate
physical parameters for stars that did not have spectroscopic data.
