Photometry and Analysis of a Sample of Quasars on Archival Yerkes Observatory Photographic Plates

We digitized a collection of several blue-sensitive plates dating from the early 1900s taken on the original 24” Ritchey reflector at Yerkes Observatory. These plates were selected to maximize the number of quasars identified in SDSS based on Galactic coordinates, exposure time, and visual assessment. We estimate the best limiting magnitudes of these plates to be g ~ 19. We then utilize two different methods to get magnitude measurements that are sufficiently precise to be useful for analyzing long-term quasar variability. Using these measurements, we determine the RMS variability of the sample for a baseline of >100 years through comparison to SDSS.