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| View Original: | Gibbous-Crescent-half-ellipse-in-circle-outlined.png (600x600) | |||
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| Keywords: Gibbous-Crescent-half-ellipse-in-circle-outlined.png Gibbous-Crescent-half-ellipse-in-circle-outlined svg A circle divided into a gibbous shape left and an astronomical crescent shape right by a half-ellipse where the major axis of the ellipse coincides with a diameter of the circle According to geometry an illuminated hemisphere of a sphere will appear to take on such gibbous or crescent shapes when viewed from an angle In this case the length of the major axis of the ellipse is twice the length of the minor axis i e the eccentricity is half the square root of 3 so that the larger gibbous area shows the theoretical shape of the visible lit area of the moon for example when the separation between the viewing angle and the angle of illumination i e between Earth and Sun is 60 degrees while the smaller crescent area shows the theoretical shape of the visible lit area of a sphere when the separation between the viewing angle and the angle of illumination is 120 degrees See also Image Gibbous-Crescent-half-ellipse-in-circle png crescent shape Astronomy sketches Hemispheres | ||||
