Solar Physics

, Volume 290, Issue 10, pp 2617–2648 | Cite as

A Novel Technique for Measuring the Solar Radius from Eclipse Light Curves – Results for 2010, 2012, 2013, and 2015

  • Philippe LamyEmail author
  • Jean-Yves Prado
  • Olivier Floyd
  • Patrick Rocher
  • Guillaume Faury
  • Serge Koutchmy


We report on a novel technique for measuring the solar radius during total solar eclipses that exploits light curves recorded just before and after second and third contacts. The measurements are performed by pre-programmed photometers that are deployed over the eclipse paths and are operated without supervision. The recorded light curves are compared to synthetic light curves calculated from high-accuracy ephemerides and lunar-limb profiles constructed from the topographic model of the Moon provided by the Kaguya lunar space mission. A minimization process between the two sets of curves yields the solar radius. Altogether, seventeen determinations have been obtained during the past four total eclipses with the following averages (at a wavelength of 540 nm and scaled to 1 AU): \(959.94\pm0.02~\mbox{arcsec}\) on 11 July 2010, \(960.02\pm0.04~\mbox{arcsec}\) on 13 November 2012, \(959.99\pm0.09~\mbox{arcsec}\) on 3 November 2013, and \(960.01\pm0.09~\mbox{arcsec}\) on 20 March 2015. Part of the differences between these four values may be attributed to weather conditions. Averaging the whole set of measurements yields a radius of \(959.99\pm0.06~\mbox{arcsec}\) (\(696{,}246\pm45~\mbox{km}\)), which agrees excellently well with the most recent data and supports an upward revision of the standard IAU value, as previously suggested.


Sun Sun: diameter Sun: eclipses 



We are grateful to Gonzague Bosch and Frédéric Bouchar of the TENUM company for their dedicated efforts to build the photometers in a very short time. We express our gratitude to Meleana Adams, Frédérique Arthaud, Charles Azymze, Jean-Pierre Barriot, Cyril Bazin, Brice Boclet, Ludovic Bousquet, Jack Brunet, Paul Castelnau, Isabelle Dhenin, Etienne Dumont, Jean-Christophe Guin, Eric Hervier, Xavier Jubier, Patrick Martinez, Jean-Claude Merlin, Jean Mouette, Alain Perret, Jason Poinot, Julie Prado, Jean-Louis Raynaud, Lydie Sichoix, and Stéphane Thomas for their participation in the deployments of the photometers, to the tour operators \(66^{\circ}\) Nord, Grand Nord Grand Large, Chasseurs d’Eclipses, and to the numerous unknown people who kindly hosted the photometers on their property. We thank Maurizio Emilio very much for providing his software to generate Figure 1. This work was supported by grants from the Centre National d’Etudes Spatiales.

Disclosure of Potential Conflicts of Interests

The authors declare that they have no conflicts of interests.


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Copyright information

© Springer Science+Business Media Dordrecht 2015

Authors and Affiliations

  • Philippe Lamy
    • 1
    Email author
  • Jean-Yves Prado
    • 2
  • Olivier Floyd
    • 3
  • Patrick Rocher
    • 4
  • Guillaume Faury
    • 1
    • 3
  • Serge Koutchmy
    • 5
  1. 1.Laboratoire d’Astrophysique de Marseille, UMR 7236CNRS & Aix-Marseille UniversitéMarseille cedex 13France
  2. 2.Centre National d’Etudes SpatialesToulouseFrance
  3. 3.AKKA Informatique et SystèmesToulouse cedex 1France
  4. 4.Institut de Mécanique Céleste et de Calcul des Ephémérides, UMR 8028CNRS & Observatoire de ParisParisFrance
  5. 5.Institut d’Astrophysique de Paris, UMR 7095CNRS & Université Pierre et Marie CurieParisFrance

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