by VictorBorun » Mon Jun 26, 2023 12:05 pm
Ann wrote: ↑Mon Jun 26, 2023 5:39 am
Let's try to make head or tails of the colors of today's APOD, shall we?
Let's begin with the Earth's rising (or setting) shadow during sunset (or sunrise). Well, shadows in clear weather on the Earth tend to be blue, right?
Shadows on white snow are blue, because they are lit up by the blue sky only. During twilight, when sunlight becomes increasingly reddened - because more and more shortwave light is filtered away, and the light that reaches us directly from the Sun is more and more deeply yellow-orange, or even red - shadows and sunlight on the ground can create an obvious blue/yellow effect.
You may have seen this sort of cloudless sunset:
I wanted to show you this sort of sunset because the sky color deepens to a clear deep red at the horizon. Not all sunsets are like this. Many are just
yellowish.
The twilight sky over San Diego is quite dark blue, but the horizon is vividly yellow and red. The color of the Belt of Venus is much paler and more diluted, but the general color scheme is the same. Yellowish sky is followed by pink (not red) sky. And then it is all interrupted by the rising (or setting) blue shadow of the Earth.
I have question. Is that billowing gray stuff seen in the middle of the APOD actually fog?
Ann
They seem to say that this APOD looks in the direction opposite to low Sun's disk.
Thinking about the colours of the sky, I try to have 2 things in mind:
1) from the centre of the disk of Sun there must be rings of red, scarlet, orangish, slightly yellow, grey, slightly cyan, bluish, indigo, violet, gaining in area and losing in brightness, summing up to total illumination to which we adapt as to current white
2) those rings are far from being concentric circles' rings. Each ring gets wider where it passes near horizon and narrower where it passes high. That explains why yellow zone is narrow above the San Diego sunset and wide at horizon
But what is the Belt of Venus, I am at loss
[quote=Ann post_id=331903 time=1687757971 user_id=129702]
Let's try to make head or tails of the colors of today's APOD, shall we?
[img3="The Belt of Venus over Mount Everest.
Image Credit & Copyright: Soumyadeep Mukherjee"]https://apod.nasa.gov/apod/image/2306/BeltofEverest_Mukherjee_960_annotated.jpg[/img3]
Let's begin with the Earth's rising (or setting) shadow during sunset (or sunrise). Well, shadows in clear weather on the Earth tend to be blue, right?
[img3="Blue shadows and yellowish sunlight during twilight. Credit: Anna Polyakova"]https://thumbs.dreamstime.com/b/shadows-snow-trunks-trees-sunset-35737707.jpg[/img3]
Shadows on white snow are blue, because they are lit up by the blue sky only. During twilight, when sunlight becomes increasingly reddened - because more and more shortwave light is filtered away, and the light that reaches us directly from the Sun is more and more deeply yellow-orange, or even red - shadows and sunlight on the ground can create an obvious blue/yellow effect.
You may have seen this sort of cloudless sunset:
[img3="A beautiful cloudless sunset. Credit: r/SanDiego_Photography by
SD_TMI"]https://preview.redd.it/pcw8oduyfcw11.jpg?auto=webp&v=enabled&s=11d7bd8703edf6f6e88bafc542835c027dcb491a[/img3]
I wanted to show you this sort of sunset because the sky color deepens to a clear deep red at the horizon. Not all sunsets are like this. Many are just [url=https://www.flickr.com/photos/photographybyderekg/6779012556]yellowish[/url].
The twilight sky over San Diego is quite dark blue, but the horizon is vividly yellow and red. The color of the Belt of Venus is much paler and more diluted, but the general color scheme is the same. Yellowish sky is followed by pink (not red) sky. And then it is all interrupted by the rising (or setting) blue shadow of the Earth.
I have question. Is that billowing gray stuff seen in the middle of the APOD actually fog?
Ann
[/quote]
They seem to say that this APOD looks in the direction opposite to low Sun's disk.
Thinking about the colours of the sky, I try to have 2 things in mind:
1) from the centre of the disk of Sun there must be rings of red, scarlet, orangish, slightly yellow, grey, slightly cyan, bluish, indigo, violet, gaining in area and losing in brightness, summing up to total illumination to which we adapt as to current white
2) those rings are far from being concentric circles' rings. Each ring gets wider where it passes near horizon and narrower where it passes high. That explains why yellow zone is narrow above the San Diego sunset and wide at horizon
But what is the Belt of Venus, I am at loss