TIME-SERIES ENSEMBLE PHOTOMETRY OF SX PHOENICIS STARS .1. BL CAMELOPARDALIS

We present an analysis of the multiperiodic SX Phoenicis star BL Camel opardalis (GD 428). Along with 24 times of maximum light from archival data, six previously unpublished times of maximum light from photomul tiplier observations and 39 new CCD observations of maximum light are reported. The new CCD observations indicate that BL Cam is a double-mo de variable with a primary period of 0.0391 day, a secondary period of 0.0306 day, and a pi(1)/pi(0) ratio of 0.783. The relation between me tallicity and period ratio for large-amplitude delta Scuti variables i s examined in detail. Finally, evidence is presented that the fundamen tal period pi(0) has increased by 0.009 s in the last 20 years.