APOD: Moonset Eclipse (2018 Feb 01)

Comments and questions about the APOD on the main view screen.
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APOD: Moonset Eclipse (2018 Feb 01)

Post by APOD Robot » Thu Feb 01, 2018 5:07 am

Image Moonset Eclipse

Explanation: Near the closest point in its orbit, the second Full Moon of the month occurred on January 31. So did the first Total Lunar Eclipse of 2018, as the Moon slid through planet Earth's shadow. In a postcard from planet Earth, this telescopic snapshot captures the totally eclipsed Moon as it set above the western horizon and the Chiricahua Mountains of southern Arizona. The Moon's evocative reddened hue is due to sunlight scattered into the shadow. Still, the planet's shadow visibly grows darker near the center, toward the top of the lunar disk.

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Re: APOD: Moonset Eclipse (2018 Feb 01)

Post by Tetenterre » Thu Feb 01, 2018 1:45 pm

Beautiful image, but surely the red light that reaches the Moon is transmitted and refracted, not scattered, by Earth's atmosphere - it is the light at the blue end of the spectrum that is scattered.

stevie

Re: APOD: Moonset Eclipse (2018 Feb 01)

Post by stevie » Thu Feb 01, 2018 2:19 pm

Does anyone know when will be the next Super Blue Black Moon Total Solar Eclipse?

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Re: APOD: Moonset Eclipse (2018 Feb 01)

Post by Chris Peterson » Thu Feb 01, 2018 2:40 pm

Tetenterre wrote:Beautiful image, but surely the red light that reaches the Moon is transmitted and refracted, not scattered, by Earth's atmosphere - it is the light at the blue end of the spectrum that is scattered.
There is minimal refraction. The light from the Sun is both scattered and absorbed in the atmosphere. The amount of scatter is wavelength dependent, with shorter wavelengths scattering differently than longer wavelengths. If the red light were not scattering, it would not be visible from the Moon. I expect you also get a redder eclipse when the Earth has lots of clouds along its terminator to scatter more light. (Just like sunsets are more obviously red when you have clouds.)
Chris

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Re: APOD: Moonset Eclipse (2018 Feb 01)

Post by neufer » Thu Feb 01, 2018 4:25 pm

Chris Peterson wrote:
Tetenterre wrote:
Beautiful image, but surely the red light that reaches the Moon is transmitted and refracted, not scattered, by Earth's atmosphere - it is the light at the blue end of the spectrum that is scattered.
There is minimal refraction. The light from the Sun is both scattered and absorbed in the atmosphere. The amount of scatter is wavelength dependent, with shorter wavelengths scattering differently than longer wavelengths. If the red light were not scattering, it would not be visible from the Moon. I expect you also get a redder eclipse when the Earth has lots of clouds along its terminator to scatter more light. (Just like sunsets are more obviously red when you have clouds.)
  • Up to 1º refraction of UNscattered 0.5º wide red sunlight around a 2º wide Earth
    + some secondary scattering & further refraction of that:
https://en.wikipedia.org/wiki/Atmospheric_refraction wrote:

<<Atmospheric refraction of the light from a star is zero in the zenith, less than 1′ (one arc-minute) at 45° apparent altitude, and still only 5.3′ at 10° altitude; it quickly increases as altitude decreases, reaching 9.9′ at 5° altitude, 18.4′ at 2° altitude, and 35.4′ at the horizon. On the horizon refraction is slightly greater than the apparent diameter of the Sun, so when the bottom of the sun's disc appears to touch the horizon, the sun's true altitude is negative.>>
https://en.wikipedia.org/wiki/Lunar_eclipse#Lunar_eclipse_appearance wrote: <<The moon does not completely disappear as it passes through the umbra because of the refraction of sunlight by the Earth's atmosphere into the shadow cone; if the Earth had no atmosphere, the Moon would be completely dark during an eclipse. The reddish coloration arises because sunlight reaching the Moon must pass through a long and dense layer of the Earth's atmosphere, where it is scattered. Shorter wavelengths are more likely to be scattered by the air molecules and the small particles, and so by the time the light has passed through the atmosphere, the longer wavelengths dominate. This resulting light we perceive as red. This is the same effect that causes sunsets and sunrises to turn the sky a reddish color; an alternative way of considering the problem is to realize that, as viewed from the moon, the sun would appear to be setting (or rising) behind the Earth.

The amount of refracted light depends on the amount of dust or clouds in the atmosphere; this also controls how much light is scattered. In general, the dustier the atmosphere, the more that other wavelengths of light will be removed (compared to red light), leaving the resulting light a deeper red color. This causes the resulting coppery-red hue of the moon to vary from one eclipse to the next. Volcanoes are notable for expelling large quantities of dust into the atmosphere, and a large eruption shortly before an eclipse can have a large effect on the resulting color.>>
Art Neuendorffer

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Re: APOD: Moonset Eclipse (2018 Feb 01)

Post by Chris Peterson » Thu Feb 01, 2018 5:41 pm

neufer wrote:
Chris Peterson wrote:There is minimal refraction. The light from the Sun is both scattered and absorbed in the atmosphere. The amount of scatter is wavelength dependent, with shorter wavelengths scattering differently than longer wavelengths. If the red light were not scattering, it would not be visible from the Moon. I expect you also get a redder eclipse when the Earth has lots of clouds along its terminator to scatter more light. (Just like sunsets are more obviously red when you have clouds.)
Up to 1º refraction of UNscattered 0.5º wide red sunlight around a 2º wide Earth
Yup. Minimal refraction. Virtually all of the red light we see on the Moon is the product of scattering, most of it from clouds and smoke particles.
Chris

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heehaw

Re: APOD: Moonset Eclipse (2018 Feb 01)

Post by heehaw » Thu Feb 01, 2018 6:00 pm

stevie wrote:Does anyone know when will be the next Super Blue Black Moon Total Solar Eclipse?
You are referring to a supercalifragilisticexpialidocious moon, of course.
Am I just being a jerk, when I say there is a full moon once every month, and ALL these stupid adjectives should be flushed?

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Re: APOD: Moonset Eclipse (2018 Feb 01)

Post by bystander » Thu Feb 01, 2018 6:05 pm

heehaw wrote: Am I just being a jerk, when I say there is a full moon once every month, and ALL these stupid adjectives should be flushed?
There is not a full moon this month!
Know the quiet place within your heart and touch the rainbow of possibility; be
alive to the gentle breeze of communication, and please stop being such a jerk.
— Garrison Keillor

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Re: APOD: Moonset Eclipse (2018 Feb 01)

Post by neufer » Thu Feb 01, 2018 6:12 pm

Chris Peterson wrote:
neufer wrote:
Chris Peterson wrote:
There is minimal refraction. The light from the Sun is both scattered and absorbed in the atmosphere. The amount of scatter is wavelength dependent, with shorter wavelengths scattering differently than longer wavelengths. If the red light were not scattering, it would not be visible from the Moon. I expect you also get a redder eclipse when the Earth has lots of clouds along its terminator to scatter more light. (Just like sunsets are more obviously red when you have clouds.)
Up to 1º refraction of UNscattered 0.5º wide red sunlight around a 2º wide Earth
Yup. Minimal refraction. Virtually all of the red light we see on the Moon is the product of scattering, most of it from clouds and smoke particles.
  • With a 2º wide Earth (and a 0.5º wide sun)
    1º of refraction is all that is needed to
    irradiate even a close umbrally eclipsed supermoon.

    Scattering augments refraction not vice versa.
https://www.etymonline.com/word/umbrage wrote:
umbrage (n.) early 15c., "shadow, shade," from Middle French ombrage "shade, shadow," from noun use of Latin umbraticum "of or pertaining to shade; being in retirement," neuter of umbraticus "of or pertaining to shade," from umbra "shade, shadow." Many figurative uses in 17c.; main remaining one is the meaning "suspicion that one has been slighted," first recorded 1610s; hence phrase to take umbrage at, attested from 1670s.
Art Neuendorffer

Gosh

Re: APOD: Moonset Eclipse (2018 Feb 01)

Post by Gosh » Thu Feb 01, 2018 6:19 pm

neufer wrote:
Chris Peterson wrote:
Tetenterre wrote:
Beautiful image, but surely the red light that reaches the Moon is transmitted and refracted, not scattered, by Earth's atmosphere - it is the light at the blue end of the spectrum that is scattered.
There is minimal refraction. The light from the Sun is both scattered and absorbed in the atmosphere. The amount of scatter is wavelength dependent, with shorter wavelengths scattering differently than longer wavelengths. If the red light were not scattering, it would not be visible from the Moon. I expect you also get a redder eclipse when the Earth has lots of clouds along its terminator to scatter more light. (Just like sunsets are more obviously red when you have clouds.)
  • Up to 1º refraction of UNscattered 0.5º wide red sunlight around a 2º wide Earth
    + some secondary scattering & further refraction of that:
https://en.wikipedia.org/wiki/Atmospheric_refraction wrote:

<<Atmospheric refraction of the light from a star is zero in the zenith, less than 1′ (one arc-minute) at 45° apparent altitude, and still only 5.3′ at 10° altitude; it quickly increases as altitude decreases, reaching 9.9′ at 5° altitude, 18.4′ at 2° altitude, and 35.4′ at the horizon. On the horizon refraction is slightly greater than the apparent diameter of the Sun, so when the bottom of the sun's disc appears to touch the horizon, the sun's true altitude is negative.>>
https://en.wikipedia.org/wiki/Lunar_eclipse#Lunar_eclipse_appearance wrote: <<The moon does not completely disappear as it passes through the umbra because of the refraction of sunlight by the Earth's atmosphere into the shadow cone; if the Earth had no atmosphere, the Moon would be completely dark during an eclipse. The reddish coloration arises because sunlight reaching the Moon must pass through a long and dense layer of the Earth's atmosphere, where it is scattered. Shorter wavelengths are more likely to be scattered by the air molecules and the small particles, and so by the time the light has passed through the atmosphere, the longer wavelengths dominate. This resulting light we perceive as red. This is the same effect that causes sunsets and sunrises to turn the sky a reddish color; an alternative way of considering the problem is to realize that, as viewed from the moon, the sun would appear to be setting (or rising) behind the Earth.

The amount of refracted light depends on the amount of dust or clouds in the atmosphere; this also controls how much light is scattered. In general, the dustier the atmosphere, the more that other wavelengths of light will be removed (compared to red light), leaving the resulting light a deeper red color. This causes the resulting coppery-red hue of the moon to vary from one eclipse to the next. Volcanoes are notable for expelling large quantities of dust into the atmosphere, and a large eruption shortly before an eclipse can have a large effect on the resulting color.>>
Does that mean the moon Trumps the earth?

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Re: APOD: Moonset Eclipse (2018 Feb 01)

Post by neufer » Thu Feb 01, 2018 7:23 pm


neufer wrote:
Chris Peterson wrote:
neufer wrote:
Up to 1º refraction of UNscattered 0.5º
wide red sunlight
around a 2º wide Earth
Yup. Minimal refraction. Virtually all of the red light we see on the Moon is the product of scattering, most of it from clouds and smoke particles.
  • With a 2º wide Earth (and a 0.5º wide sun)
    1º of refraction is all that is needed to
    irradiate even a close umbrally eclipsed supermoon.
    Scattering augments refraction not vice versa.
Gosh wrote:
Does that mean the moon Trumps the earth?
Art Neuendorffer

heehaw

Re: APOD: Moonset Eclipse (2018 Feb 01)

Post by heehaw » Thu Feb 01, 2018 8:17 pm

bystander wrote:
heehaw wrote: Am I just being a jerk, when I say there is a full moon once every month, and ALL these stupid adjectives should be flushed?
There is not a full moon this month!
Touché! And here I am, Mr. Calendar! http://hankehenryontime.com/html/today.html

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Re: APOD: Moonset Eclipse (2018 Feb 01)

Post by MarkBour » Thu Feb 01, 2018 8:32 pm

neufer wrote:
I wondered if there were actual images of this, as opposed to the simulated image in that Wikipedia article.
What I was able to locate on the Web : Philosophically speaking, we witness a Solar eclipse by the Earth every night, right here at home.
Mark Goldfain

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Re: APOD: Moonset Eclipse (2018 Feb 01)

Post by BillBixby » Thu Feb 01, 2018 9:51 pm

Touché! And here I am, Mr. Calendar! http://hankehenryontime.com/html/today.html[/quote]

I guess I fail to understand the linked calendar. It says today is Thursday, Feb second.
My calendar says today is Thursday, Feb first. Is there humor involved?

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Re: APOD: Moonset Eclipse (2018 Feb 01)

Post by Chris Peterson » Thu Feb 01, 2018 9:59 pm

BillBixby wrote:
Touché! And here I am, Mr. Calendar! http://hankehenryontime.com/html/today.html
I guess I fail to understand the linked calendar. It says today is Thursday, Feb second.
My calendar says today is Thursday, Feb first. Is there humor involved?
http://hankehenryontime.com/html/calendar.html
Chris

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BillBixby
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Re: APOD: Moonset Eclipse (2018 Feb 01)

Post by BillBixby » Thu Feb 01, 2018 10:02 pm

BillBixby wrote:Touché! And here I am, Mr. Calendar! http://hankehenryontime.com/html/today.html
I guess I fail to understand the linked calendar. It says today is Thursday, Feb second.
My calendar says today is Thursday, Feb first. Is there humor involved?[/quote]

Now I went on-line and found this calendar is a proposed improved remodel of our current working calendar.

Gosh

Re: APOD: Moonset Eclipse (2018 Feb 01)

Post by Gosh » Fri Feb 02, 2018 12:55 am

BillBixby wrote:
BillBixby wrote:Touché! And here I am, Mr. Calendar! http://hankehenryontime.com/html/today.html
I guess I fail to understand the linked calendar. It says today is Thursday, Feb second.
My calendar says today is Thursday, Feb first. Is there humor involved?
Now I went on-line and found this calendar is a proposed improved remodel of our current working calendar.[/quote]

Blame the groundhog.

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Re: APOD: Moonset Eclipse (2018 Feb 01)

Post by Boomer12k » Fri Feb 02, 2018 1:53 am

Great image... I wish I would have had the good weather... but it was overcast, and misty out....

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Re: APOD: Moonset Eclipse (2018 Feb 01)

Post by Guest » Fri Feb 02, 2018 2:50 am

So I was trying to explain to the kids why the moon (and planets, etc) are round. I ran into a problem trying to explain why gravity works without expending energy. Esp since the patent office clearly states that a perpetual energy machine is not possible.

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Re: APOD: Moonset Eclipse (2018 Feb 01)

Post by neufer » Fri Feb 02, 2018 5:33 am


Guest wrote:
So I was trying to explain to the kids why the moon (and planets, etc) are round. I ran into a problem trying to explain why gravity works without expending energy.
The moon (and planets, etc) aren't entirely round.

If they are rotating, centrifugal force turns them into oblate spheroids.

And on Earth, light continental plates & mountains of granite float on a semi-liquid asthenosphere like icebergs.

The important thing is that all the semi-liquid pressures at depth must balance out according to Pascal's Law.
Art Neuendorffer