A new differential variable-star photometry system has been designed, constructed, and tested at the Rothney Astrophysical Observatory of the University of Calgary. The system uses a single telescope, photometer, and detector and consists of gated pulse-counting electronics synchronized to a chopped secondary mirror. The mirror is driven to four positions, permitting rapid alternate detection of a variable star, comparison star, and two sky-background regions. Within certain constraints the system is insensitive to the effects of transparency, sky-brightness, and detector-sensitivity variations occurring on time scales longer than the system’s duty cycles. The system has proved effective under as much as three magnitudes of cloud and attendant sky-brightness variation.
© 1982 Optical Society of America
E. F. Milone, R. M. Robb, F. M. Babott, and C. H. Hansen, "Rapid alternate detection system of the Rothney Astrophysical Observatory," Appl. Opt. 21, 2992-2995 (1982)