ECLIPSES, SOLAR LIMB DARKENING FUNCTION AND DIAMETER MEASUREMENTS: TOWARD A UNIFIED APPROACH

Abstract

In order to perform high resolution astrometry of the solar diameter from the ground, through the observations of eclipses, the study of the limb darkening profile is described. Knowing the profile of the solar limb is useful both to monitor the solar radius over time, and to define the oblateness, which is interesting for the classical tests of general relativity. The Limb Darkening Function (LDF) is studied in order to find the inflexion point, to which the measurements of the solar diameter are referred. The proposed method is applied to the videos of the annular eclipse in January, 15, 2010. This new method might solve the ambiguity of some eclipse obervations made with different instruments, where the measured solar diameter was clearly dependent on the aperture of the telescope and on the density of the filter used.