THE MOON 107 Now, since the projection of the lune GBHD on the disc, presented to the observer is the crescent seen by the observer, the breadth of the crescent is evidently = r(l — cos 0), where #= L BMD and ;• is the radius of the disc. But<9 = 180°-angleEMS = the exterior angle subtended at M by… … Fig. 52. Hence, we conclude that when EMS = 180°, i.e., M is between the earth and the sun, the phase is zero. This is called the New Moon. When the angle EMS = 90° (i.e., at first and third quarters), the phase is half (and the breadth of the illumi- nated portion =/•). Finally, when the angle EMS…
Astronomy
Internet Archive · Gerstein - University of Toronto · Public domain (published before 1931). Free to use for anything.
