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Starfinder (Diolaiti et al. 2000) is a code designed to analyze Adaptive Optics (AO) images of crowded stellar fields.

A typical AO observation is characterized by a well sampled and complex shaped Point Spread Function (PSF), with a sharp central peak, an extended halo and several features. A convenient approach to handle such a PSF is to use a numerical model, without any analytic approximation. The flux and position of a given star (or point-like source) are estimated by matching its image with a scaled and shifted copy of the PSF model. Starfinder can also account for a spatially variable background in the image.

Methods to model the PSF when it cannot be considered constant across the field of view have been studied in Schreiber et al. 2011 and Schreiber et al. 2012. Some of these have been implemented in Starfinder: a) piece-wise constant PSF, where the image is analyzed considering local PSF estimates in different sub-domains; b) parametric PSF models (e.g. multi-Moffat functions), with variable parameters across the field of view.

Left. Galactic Center image (Ks band) taken with PUEO on the CFHT (courtesy François Rigaut). Right. Image model produced by Starfinder, including a copy of the PSF for each detected star plus a smooth background.
















The Starfinder code has been developed in Interactive Data Language® (IDL).

IDL users may want to run it from command line. The main routine is contained in the file “” included in the package.

A simple Graphical User Interface is also available, which can be started by entering the “xstarfinder” command at the IDL prompt, once the code has been installed. The GUI version does not include all the code features.

The Starfinder code can be downloaded here.

Please send information requests and bug reports to:
Emiliano Diolaiti (
Laura Schreiber (

Copyright and references

The StarFinder software is provided “as is” without express or implied warranty.
It can be used freely for research and educational purposes.

Please reference the authors in any publication resulting from the use of the StarFinder code. The references to be cited are:

  • Diolaiti E., Bendinelli O., Bonaccini D., Close L.M., Currie D.G., Parmeggiani G., Astronomy & Astrophysics Supplement Series, 147, 335, 2000
  • Schreiber L., Diolaiti E., Bellazzini M., Ciliegi P., Foppiani I., Greggio L., Lanzoni B., Lombini M., Second International Conference on Adaptive Optics for Extremely Large Telescopes, Online at, id.P57, Bibliographic Code 2011aoel.confP..57S, 2011

Other information

The recent developments of the Starfinder code have been supported by a “TECNO-INAF 2010” grant from Istituto Nazionale di Astrofisica.

In the framework of the TECNO-INAF 2010 grant, the DIBRIS department at the University of Genova have developed a software package for image restoration with spatially variable PSF, called PATCH.