CALIBRATION OF THE UBVRI HIGH-SPEED PHOTOMETER OF LABORATORIO-NACIONAL-DE-ASTROFISICA, BRAZIL

We describe the characteristics and performance of a high-speed multic olor photometer, FOTRAP, which has been used since 1988 at LNA, Labora torio Nacional de Astrofisica/CNPq, Brazil. The optomechanical concept s, electronics, and software are outlined. We discuss the quality and consistency of the transformations from the natural system to the UBVR I standard system. We give particular attention to the problem of tran sforming to the standard system observations of objects with blue spec tra, like cataclysmic variables. We compare the results of our UBVRI m easurements for a few spectrophotometric standards with the values pub lished in the literature.