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APOD: Embraced by Sunlight (2022 Feb 03)
Posted: Thu Feb 03, 2022 5:05 am
by APOD Robot
Embraced by Sunlight
Explanation: Even though Venus (left) was the brightest planet in the sky it was less than 1/30th the apparent size of the Moon on January 29. But as both rose before the Sun they shared a crescent phase. For a moment their visible disks were each about 12 percent illuminated as they stood above the southeastern horizon. The similar sunlit crescents were captured in
these two separate images. Made at different magnifications, each panel is a composite of stacked video frames taken with a small telescope. Venus goes through a range of
phases like the Moon as the inner planet wanders from
evening sky to morning sky and back again with a period of 584 days.
Of course the Moon completes its own cycle of phases, a full lunation, in about
29.5 days.
Re: APOD: Embraced by Sunlight (2022 Feb 03)
Posted: Thu Feb 03, 2022 12:24 pm
by Roger Venable
In these two images, though both Venus and the Moon are nominally illuminated in the same percentage of their Earth-facing hemispheres, the cusps of Venus appear to extend further toward the north and south extremes than those of Luna do. This is not an illusion. Venus has an upper layer of thin clouds that exhibit forward scattering, making the cusps appear brighter than would be expected with the illumination of a smooth sphere. In contrast, Luna's rough surface does not scatter forward, and actually partially shadows the terminator, making the cusps appear darker than would be expected with the illumination of a smooth sphere. This effect is even more pronounced with crescents of the two bodies are thinner than those presented in these images. Sometimes when very close to inferior conjunction a faint but complete ring of light can be seen around Venus, while near new moon each month the visible part of the lunar crescent appears very diminished, often to less than 90 degrees of the lunar circumference.
Re: APOD: Embraced by Sunlight (2022 Feb 03)
Posted: Thu Feb 03, 2022 12:32 pm
by orin stepanek
Venus; Venus shine so bright;
Early before the morning light!
Re: APOD: Embraced by Sunlight (2022 Feb 03)
Posted: Thu Feb 03, 2022 9:40 pm
by johnnydeep
Roger Venable wrote: ↑Thu Feb 03, 2022 12:24 pm
In these two images, though both Venus and the Moon are nominally illuminated in the same percentage of their Earth-facing hemispheres, the cusps of Venus appear to extend further toward the north and south extremes than those of Luna do. This is not an illusion. Venus has an upper layer of thin clouds that exhibit forward scattering, making the cusps appear brighter than would be expected with the illumination of a smooth sphere. In contrast, Luna's rough surface does not scatter forward, and actually partially shadows the terminator, making the cusps appear darker than would be expected with the illumination of a smooth sphere. This effect is even more pronounced with crescents of the two bodies are thinner than those presented in these images. Sometimes when very close to inferior conjunction a faint but complete ring of light can be seen around Venus, while near new moon each month the visible part of the lunar crescent appears very diminished, often to less than 90 degrees of the lunar circumference.
I think I follow your reasoning here, but I honestly don't seen any difference in the extent of the Moon's and Venus' cusps in this APOD.
Re: APOD: Embraced by Sunlight (2022 Feb 03)
Posted: Fri Feb 04, 2022 12:21 am
by Fred the Cat
Apparent size from
Earth embraces the perspective.
Re: APOD: Embraced by Sunlight (2022 Feb 03)
Posted: Fri Feb 04, 2022 2:29 am
by neufer
johnnydeep wrote: ↑Thu Feb 03, 2022 9:40 pm
Roger Venable wrote: ↑Thu Feb 03, 2022 12:24 pm
In these two images, though both Venus and the Moon are nominally illuminated in the same percentage of their Earth-facing hemispheres, the cusps of Venus appear to extend further toward the north and south extremes than those of Luna do. This is not an illusion. Venus has an upper layer of thin clouds that exhibit forward scattering, making the cusps appear brighter than would be expected with the illumination of a smooth sphere. In contrast, Luna's rough surface does not scatter forward, and actually partially shadows the terminator, making the cusps appear darker than would be expected with the illumination of a smooth sphere. This effect is even more pronounced with crescents of the two bodies are thinner than those presented in these images. Sometimes when very close to inferior conjunction a faint but complete ring of light can be seen around Venus, while near new moon each month the visible part of the lunar crescent appears very diminished, often to less than 90 degrees of the lunar circumference.
I think I follow your reasoning here,
but I honestly don't seen any difference in the extent of the Moon's and Venus' cusps in this APOD.
https://en.wikipedia.org/wiki/Venus#Ashen_light wrote:
<<A long-standing mystery of Venus observations is the so-called ashen light—an apparent weak illumination of its dark side, seen when the planet is in the crescent phase.
The first claimed observation of ashen light was made in 1643, but the existence of the illumination has never been reliably confirmed. Observers have speculated it may result from electrical activity in the Venusian atmosphere, but it could be illusory, resulting from the physiological effect of observing a bright, crescent-shaped object.>>
Re: APOD: Embraced by Sunlight (2022 Feb 03)
Posted: Fri Feb 04, 2022 2:43 pm
by johnnydeep
neufer wrote: ↑Fri Feb 04, 2022 2:29 am
johnnydeep wrote: ↑Thu Feb 03, 2022 9:40 pm
Roger Venable wrote: ↑Thu Feb 03, 2022 12:24 pm
In these two images, though both Venus and the Moon are nominally illuminated in the same percentage of their Earth-facing hemispheres, the cusps of Venus appear to extend further toward the north and south extremes than those of Luna do. This is not an illusion. Venus has an upper layer of thin clouds that exhibit forward scattering, making the cusps appear brighter than would be expected with the illumination of a smooth sphere. In contrast, Luna's rough surface does not scatter forward, and actually partially shadows the terminator, making the cusps appear darker than would be expected with the illumination of a smooth sphere. This effect is even more pronounced with crescents of the two bodies are thinner than those presented in these images. Sometimes when very close to inferior conjunction a faint but complete ring of light can be seen around Venus, while near new moon each month the visible part of the lunar crescent appears very diminished, often to less than 90 degrees of the lunar circumference.
I think I follow your reasoning here,
but I honestly don't seen any difference in the extent of the Moon's and Venus' cusps in this APOD.
https://en.wikipedia.org/wiki/Venus#Ashen_light wrote:
<<A long-standing mystery of Venus observations is the so-called ashen light—an apparent weak illumination of its dark side, seen when the planet is in the crescent phase.
The first claimed observation of ashen light was made in 1643, but the existence of the illumination has never been reliably confirmed. Observers have speculated it may result from electrical activity in the Venusian atmosphere, but it could be illusory, resulting from the physiological effect of observing a bright, crescent-shaped object.>>
Very interesting: "Things that make you go 'hmm'".
