Optical STJ observations of the Crab Pulsar

We report the first observations Of an astronomical object using a supercon ducting tunnel junction (STJ) device, a pixel detector with intrinsic energ y resolution in the optical wavelength range. The Crab pulsar was observed using a 6 x 6 array of Tantalum STJs at the 4.2-m William Herschel Telescop e on La Palma, Each array element provides photon counting capability recor ding up to similar to 10(3) photons pix(-1) s(-1) with an arrival time accu racy of about 5 mu s, and providing a wavelength resolution of about 100 nm . We derive a photometrically resolved light curve which, however, shows no significant colour index variations with pulsar phase.