A Double-Head Photon-Counting Photometer for Fast Timing Observations

The structure of the electronics of the two head, high speed photometer, operating on the 152 cm G.D. Cassini telescope of Bologna University has been fully redesigned for high-time-resolution observations of fast variable cosmic sources, in particular, of the optical counterparts of X-ray binary systems. The fast photometer now permits sampling times from 0.1 ms to 100 s. The handling of the system clock and I/O configuration have been modified to provide rigorous synchronization of the sampling time with an external high-stability clock and the continuous of an uninterrupted data stream. The continuous data acquisition process, which is driven by an external clock, is limited only by the capacity of the hard disk and is supported by a double-buffer SRAM memory designed to overcome any discontinuity in the asynchronous communication with the computer. Real-time monitoring of the data enables continuous evaluation of the weather conditions, and the directly displayed light-curve, can be used to determine the optimal management of the observations.