Fine structure of the celestial polarization pattern and its temporal change during the total solar eclipse of 11 August 1999

Using 180 degrees field-of-view (full-sky) imaging polarimetry, we measured the spatiotemporal change of the polarization pattern of the entire celest ial hemisphere during the total solar eclipse of ii August 1999 in Kecel, H ungary. We compared these patterns with the normal celestial polarization p atterns measured at the same times on the subsequent day of the eclipse. As a second control sky, the celestial polarization pattern measured on 26 Au gust 1999 in Tunisia was chosen with the same solar zenith distance as that at the Hungarian eclipse. We computed the corresponding theoretical celest ial polarization patterns on the basis of the single-scattering Rayleigh mo del. The spectral characteristics of the polarization pattern in the sky du ring totality were also measured in the red (650 nm), green (550 nm), and b lue (450 nm) ranges of the spectrum. A qualitative explanation was given fo r the origin of the angle of polarization (E-vector) pattern and the neutra l point of skylight polarization near the zenith observed Juring totality. The I elation of our results to earlier observations on skylight polarizati on during total eclipses was analyzed. The agreements with previous eclipse observations were discussed. The reasons for some disagreements with previ ous eclipse observations were explained in connection with the spectral dep endence of skylight polarization and the fine structure of the celestial E- vector pattern during totality. (C) 2001 Elsevier Science Tnc. All rights r eserved.