A&A 461, 373-379 (2007)
DOI: 10.1051/0004-6361:20042505

A deconvolution-based algorithm for crowded field photometry with unknown point spread function

P. Magain¹, F. Courbin², M. Gillon^{3, 1}, S. Sohy¹, G. Letawe¹, V. Chantry¹, and Y. Letawe<sup>1

1</sup>  Institut d'Astrophysique et de Géophysique, Université de Liège, allée du 6 Août 17, 4000 Liège, Belgium
    e-mail: Pierre.Magain@ulg.ac.be
²  École Polytechnique Fédérale de Lausanne (EPFL), Laboratoire d'Astrophysique, Observatoire, 1290 Sauverny, Switzerland
³  Observatoire de Genève, 51 Chemin des Maillettes, 1290 Sauverny, Switzerland

(Received 8 December 2004 / Accepted 5 September 2006)

Abstract
A new method is presented for determining the point spread function (PSF) of images that lack bright and isolated stars. It is based on the same principles as the MCS image deconvolution algorithm. It uses the information contained in all stellar images to achieve the double task of reconstructing the PSFs for single or multiple exposures of the same field and to extract the photometry of all point sources in the field of view. The use of the full information available allows us to construct an accurate PSF. The possibility to simultaneously consider several exposures makes it well suited to the measurement of the light curves of blended point sources from data that would be very difficult or even impossible to analyse with traditional PSF fitting techniques. The potential of the method for the analysis of ground-based and space-based data is tested on artificial images and illustrated by several examples, including HST/NICMOS images of a lensed quasar and VLT/ISAAC images of a faint blended Mira star in the halo of the giant elliptical galaxy NGC 5128 (Cen A).

Key words: techniques: image processing -- techniques: photometric

© ESO 2006

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