Abstract:The efficiency with which a charge-coupled device (CCD) detects photons depends, amongst other factors, on where within a pixel the photon hits. To explore this effect we have made detailed scans across a pixel for a front-illuminated three-phase EEV05-20 CCD using the standard astronomical B, V, R, and I colour filters. Pixel response functions and photometric sensitivity maps are derived from the scan images. Nonlinear charge transfer inefficiency (CTI) effects were observed and corrected for. The resulting images clearly show the intra-pixel sensitivity variations (IPSVs) due to the CCD electrode structure, and its dependence on wavelength. We briefly comment on the implications of IPSVs and CTI for high-precision photometry and astrometry.

We report on the current status of the University of New South Wales Extrasolar Planet Search project, giving details of the methods we use to obtain millimagnitude precision photometry using the 0.5‐m Automated Patrol Telescope. We use a novel observing technique to optimally broaden the point spread function and thus largely eliminate photometric noise due to intrapixel sensitivity variations on the CCD. We have observed eight crowded Galactic fields using this technique during 2003 and 2004. Our analysis of the first of these fields (centred on the open cluster NGC 6633) has yielded 49 variable stars and four shallow transit candidates. Follow‐up observations of these candidates have identified them as eclipsing binary systems. We use a detailed simulation of our observations to estimate our sensitivity to short‐period planets, and to select a new observing strategy to maximize the number of planets detected.