ATMOSPHERIC EXTINCTION: CZECH LUNAR PHOTOMETRY OF THE JUNE 25, 1964 ECLIPSE

Abstract

eclipses for the purpose of determining the excess of atmospheric extinction due to an apparently large amount of volcanic dust spread over the upper atmosphere after the eruption of Mount Agung, Bali, on March 17, 1963. The total eclipse of June 25, 1964 was not observable from Iowa, but Bouska and Mayer (1965) published the results of their photoelectric observations in the visual region which provide useful data for further comparison with the above calculations. Figure 1, which has been redrawn from Figure 3 of Paper I to include their observations, suggests that 25 km is a better assumption for the maximum height of the dust layers. The values of s, the fraction of dust extinction in terms of the usual extinction coefficient, estimated for the three eclipses are 0.20, 0.15, and 0.11 mag. per air mass for the December 1963, June 1964, and December 1964 eclipses, respectively. The corresponding value for the normal atmosphere ranges from about 0.065 at A 5500 ( Allen 1963 ) to 0.045 mag. per air mass ( Moreno, Sanduleak, and Stock 1965 ) . Hence, the excess in the extinction coefficients due to additional dust may be estimated as 0.145, 0.095, and 0.055 mag. per air mass for the three dates. We can then obtain the total extinction for each