HST Photometry of Dense Globular

It is shown that in very crowded elds, such as the cores of globular clusters, aperture pho-tometry of subsampled-deconvolved HST/WFPC2 images gives statistically better results than any of the following DAOPHOT-II reductions of the original data: aperture photometry, proole-tting photometry, and the hybrid method of aperture photometry on neighbour-subtracted images. Furthermore , the deconvolved images also provide the basis for improved star detection, using otherwise conventional means. These conclusions are developed and illustrated using both real HST/WFPC2 data of the Milky Way bulge globular cluster NGC 6293 in the F555W and F814W bands, and realistic simulations of a globular cluster observed under similar circumstances. The results are a consequence of exploiting the nature of the HST/WFPC2 point-spread function (PSF): undersampled, spatially varying and with high-frequency structure in the wings, but determinable to high accuracy by subsam-pled spatially-varying modelling of rst-guess Tiny Tim grids followed by empirical improvements.