A Package for the Reduction of Dithered Undersampled Images

We present a set of tasks developed to process dithered undersampled images. These procedures allow one to easily determine the osets between images and then combine the images using Variable-Pixel Linear Reconstruction, otherwise know as \drizzle". This algorithm, originally developed for the combination of the images in the Hubble Deep Field(Williams et al. 1996, Fruchter & Hook 1997), preserves photometry and resolution, can weight input images according to the sta- tistical signicance of each pixel, and removes the eects of geometric distortion both on image shape and photometry. In this paper, the method and its implementation are described, and measurements of the photometric accuracy and image delity are presented. In addition, we describe ancillary tasks developed for determining osets between images, and discuss the use of drizzling to combine dithered images in the presence of cosmic rays.