Abstract
The total solar irradiance varies over a solar cycle of 11 years and maybe over cycles of longer periods. Is the solar diameter variable over time too? A discussion of the solar diameter and its variations must be linked to the limb darkening function (LDF). We introduce a new method to perform high-resolution astrometry of the solar diameter from the ground, through the observations of eclipses, using the luminosity evolution of Baily’s bead and the profile of the lunar edge available from satellite data. This approach unifies the definition of the solar limb with the inflection point of LDF for eclipses and drift-scan or heliometric methods. The method proposed is applied for the videos of the eclipse on 15 January 2010 recorded in Uganda and in India. The result suggests reconsidering the evaluations of the historical eclipses observed with the naked eye.
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Notes
Dealing with the radius is equivalent to dealing with the diameter, but in this work we refer to the former or to the latter depending on the context.
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This research has made use of the data taken with the LALT instrument on board the lunar orbiter Kaguya of JAXA/SELENE.
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Raponi, A., Sigismondi, C., Guhl, K. et al. The Measurement of Solar Diameter and Limb Darkening Function with the Eclipse Observations. Sol Phys 278, 269–283 (2012). https://doi.org/10.1007/s11207-012-9947-2
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DOI: https://doi.org/10.1007/s11207-012-9947-2