crescent phase
The collective term for the phases of a celestial body when it is less than 50% illuminated. It most often refers to the Moon, but is also applied to the inferior planets.
D ...
Crescent Phase - The phase of the moon at which only a small, crescent-shaped portion of the near side of the Moon is illuminated by sunlight. Crescent phase occurs just before and after new moon ...
When the angular distance is less than 90° separation, you on the Earth will see less than half of the Moon's illuminated (day) side and it will look like a a curved sliver of light---the crescent phase.
Venus seems much larger in its crescent phase than when it is full because it is much closer to us during its crescent phase.
Also, since the Moon in a crescent phase--either waxing or waning--is close to the Sun on the sky, it can't be above the horizon at night unless it's shortly after sunset or before sunrise.
A long-standing mystery of Venus observations is the so-called 'ashen light'â€"an apparent weak illumination of the dark side of the planet, seen when the planet is in the crescent phase.
Thus, as the following diagrams indicate, in the Ptolemaic system Venus should always be in crescent phase as viewed from the Earth because as it moves around its epicycle it can never be far from the direction of the sun (which lies beyond it), ...
Planet or Moon appears in crescent phase when nearly between observer and sun.
Phases of Illumination ...
Maximum brilliance (a stellar magnitude of -4.4, or 15 times the brightest star) is seen in the crescent phase. The phases and positions of Venus in the sky repeat with the synodic period of 1.6 years.
In the case of Venus, observations during the crescent phase often reveal that the unlit portion is still emitting some light - this phenomenon is known as the ashen light, and is currently unexplained.
A faint glow from the unlit side of Venus when it is in the crescent phase. Its cause is unknown; it may be the Venusian analog to terrestrial airglow. [H76]
Asinh Magnitude ...
Earthshine. The faint luminosity seen of the night side of the Moon, especially when the Moon appears at a crescent phase. It is caused by light reflected from the Earth onto the Moon.
earthshine: sunlight reflected by Earth that makes the otherwise dark part of the Moon glow faintly. It's especially obvious during the Moon's thin crescent phases.
approaches its New Moon phase, only a decreasingly thin crescent remains (position H in the diagram below). The waning (shrinking) crescent Moon rises after midnight, transits the meridian after sunrise and sets after noon. The waning crescent phase ...
The crescent will start out very thin and fatten up as the Moon moves farther away from the Sun. (Note: although the Moon is closer to the Sun during new and crescent phases, it is still 400 times closer to Earth; i.e.
Venus comes closer to the Earth than any other planet, and appears to be the second brightest object in the night sky. Because of its closeness, astronomers on Earth can easily see the phases of Venus with binoculars. The new crescent phase appears ...
We shall merely note some points which are frequently overlooked: (i) the crescent phase of the moon is shown only when the moon is less than 90° from the sun; (2) the bright convex outline of the crescent is then on the side toward the sun, ...
 See also: Phase, Earth, Sun, Crescent, Light
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