Superconducting cameras for optical astronomy

Superconducting Tunnel Junctions (STJs) have been extensively investigated as photon detectors covering the range from near-infrared to X-ray energies. A 6x6 array of Tantalum junctions has already been used in an optical spectra-photometer. With this camera, the European Space Agency has performed multiple astronomical observations of optical sources using the William Herschel 4.2m telescope at La Palma. Following the success of this programme, we are now developing a second generation camera. The goals of this programme are to increase the field of view of the instrument from 4"x4" to 10.5"x9", to optimize IR rejection filters, possibly extending the 'red' response to similar to1 um and to increase the electronics readout speed. For these purposes, we are developing a new Superconducting Tunnel Junction Array consisting of 10x12 Tantalum/Aluminium devices as well as an improved readout system. In this paper, we review the instrument's architecture and describe the performance of the new detector.