Jones, H. Spencer (Harold Spencer), 1890- · London E. Arnold & co. · leaf 91
parentoutline of the Moon is therefore formed of a semicircle and asemi-ellipse, the semicircle portion being the boundary facingthe Sun : the common diameter of the semi-eUipse and thesemicircle is perpendicular to the plane containing the Sun,Earth and Moon. A portion of a sphere, such as PGQBP,… … Fig. 29.- -Shape of Visible LunarCrescent. THE MOON 79 visible portion of the Moons surface is therefore a lune whoseangle is equal to the angle subtended by the Sun and Moon atthe Earth. When the Earth is between the Sun and the Moon the angleBOD becomes zero. In that case the whole of the…
Astronomy
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