Solar limb brightening at the extreme limb from photoelectric eclipse observations

Abstract

Photoelectric observations of the light intensity from the solar crescent before and after totality were made during the eclipses of 7 March, 1970 and 26 February, 1979. Effective wavelengths were determined by interference filters of 20 nm bandwidth. To obtain the limb darkening function, the resulting intensity curves were analyzed by an extension of the method of Julius in which we take into account the actual lunar limb profile. The limb darkening function at 433 nm was obtained for the region 0.937 < sin θ < 0.9999. Our results are in good agreement with existing center-to-limb measurements in the region of overlap which extends to sin θ = 0.99. Additional data were obtained at 600 nm for 0.994 < sin θ < 0.9999. The curves at both wavelengths show a distinctive limb brightening effect at sin θ = 0.999.