WFPC images offer a wide field of view but significantly undersample the PSF. A strategy to recover some of the resolution lost by undersampling is to split the exposure time into several images, which are shifted by a fraction of the pixel size. These images can subsequently be combined with a modified Richard-Lucy algorithm. One of the challenges of this approach is the treatment of cosmic ray hits. A procedure to simultaneously co-add images with different PSFs in the presence of CR hits is presented here. An IRAF implementation (Freudling, 1993) was tested on both simulations and real WFPC data. These tests show the viability of the proposed strategy.
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