An algorithm to smooth and find objects in astronomical images

Abstract

An algorithm that uses only integer arithmetic to smooth edges and intensities and find the edges of objects is described. Multiple passes through an image are used. Objects are defined by size and threshold criteria; the threshold criterion used varies locally in the image. The algorithm incorporates intensity smoothing to reduce the effects of noise in the data. Results of a FORTRAN implementation designed to test the algorithm on digital astronomical images are discussed. The ability of the implementation to find objects is evaluated by comparing the objects and centers found with those found by the photometric reduction program DAOPHOT (Stetson 1987).