A&A Supplement series, Vol. 127, February I 1998, 587-595

Received April 14; accepted June 4, 1997

Discrimination of point-like objects in astronomical images using surface curvature

A. Llebaria - P. Lamy - P. Malburet

Send offprint request: A. Llebaria
Laboratoire d'Astronomie Spatiale du CNRS, BP. 8, F-13376 Marseille Cedex 12, France

Abstract:

We present a method for the discrimination of point-like objects in astronomical images using surface curvature. The principal curvatures k₁ and k₂ are calculated using a local quadric approximation to the log of the intensity of the original image. The analysis of the (k₁, k₂) diagram allows to easily separate various shapes and to establish a criterion for discrimination. A mask is then generated and the invalid pixels are replaced by a local, pyramidal interpolation using a non-linear, multiresolution method. We present two applications, the discrimination and removal of stars from the dust tail of comet P/Halley observed while it was crossing the Milky Way, and the removal of cosmic ray impacts from images of the solar corona obtained with a space-coronagraph.

keywords: techniques: image processing -- comets: general; P/Halley -- sun: corona

• 1. Introduction
• 2. Method
• 3. Discrimination of point-like objects on the (k₁, k₂) diagram
• 4. Restoration of the background
• 5. Two practical applications
• 6. Conclusion
• References