Solar Physics

, Volume 281, Issue 2, pp 863–875 | Cite as

Identification of Sunspots on Full-Disk Solar Images Using Wavelet Analysis

  • D. Djafer
  • A. Irbah
  • M. Meftah


A new method to detect sunspots on full-disk solar images, recorded in an optical wide spectral band and in the line of Ca ii K1, is presented. It is based on the compact wavelet transform and a process that automatically identifies the noise in the images of the Sun. This method estimates also its center and the limb positions with a precision of a few milliarcseconds. Precisions of 1 and 8 milliarcseconds are, respectively, found for the disk center position and the radius of simulated solar images. The results obtained on sunspot identification on solar images recorded during April 2002 at Meudon Observatory (France) reveal that we are able to detect 3.35 % additional sunspots compared to a manual method. Our method preserves the sunspot areas better than 95 %.


Edge detection Gaussian filters Sunspots Sun radius Wavelet analysis 



This work has been developed with the support of Centre National d’Etudes Spatiales (France), CNRS, and the French Foreign Affair Ministry under the framework of scientific cooperation contract TASSILI between France and Algeria.


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Copyright information

© Springer Science+Business Media B.V. 2012

Authors and Affiliations

  1. 1.Unité de Recherche Appliquée en Energies RenouvelablesGhardaïaAlgérie
  2. 2.Laboratoire Atmosphères, Milieux, Observations Spatiales, CNRS: UMR8190Université Paris VI–Pierre et Marie Curie–Université de Versailles Saint-Quentin-en-Yvelines–INSUGuyancourtFrance

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