Fabry-Perot observations using a new GaAs photon-counting system

A third-generation image photon-counting system (IPCS) camera is presented, based on a GaAs photocathode that can achieve a quantum efficiency of up to 23%, which is comparable to a thick CCD but without readout noise. This system is 10 times more sensitive at H than previous photon-counting cameras. In terms of signal-to-noise ratio, the system outperforms CCDs for extremely faint fluxes, including antireflection-coated, low-noise, thin CCDs. This system, with up to 1K x 1K pixels, is one of the largest monolithic IPCSs. A unique cooling system, based on a Ranque-Hilsh vortex tube, is used for this camera. Real-time centering is done by a scalable digital signal processor board. Astrophysical projects and preliminary results obtained with this new camera coupled with a scanning Fabry-Perot interferometer at the Cassegrain focus of the 3.6 m ESO telescope, the 1.93 m Observatoire de Haute Provence telescope, and the 1.6 m Observatoire du Mont Megantic telescope are presented.