ABSTRACT
This chapter examines the solar and lunar eclipses, and the occultations of the stars by the Moon. The treatment will be limited essentially only to the geometric aspect, even if eclipses also have important physical implications. The solar eclipses also deserve the merit of having permitted the discovery of the very hot solar corona by visual observations. Solar eclipses occur when the Moon passes in front of the Sun, therefore necessarily around new moon phases. The particular geometric circumstances produce total or partial penumbral, and total or partial umbral eclipses. Scattering of the solar light by clouds of the Earth's atmosphere is obviously present also outside the eclipses, and it is seen as a faint gray illumination beyond the terminator; because of its color, it is usually called ashen light. The precise calculation of the circumstances of the solar and lunar eclipses can be made with a method devised by Bessel.
