APOD: Moonset Eclipse (2018 Feb 01)

[APOD Robot]

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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[Tetenterre]

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]

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

[Chris Peterson]

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.)

[neufer]

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:

---

<<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.>>

[b][color=#FF0000]From the Moon, a lunar eclipse would show a ring of reddish-orange light surrounding a dark Earth in the sky.[/color][/b]

---

<<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.>>

[Chris Peterson]

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.

[heehaw]

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?

[bystander]

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!

[neufer]

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.

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.

[Gosh]

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:

---

<<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.>>

[b][color=#FF0000]From the Moon, a lunar eclipse would show a ring of reddish-orange light surrounding a dark Earth in the sky.[/color][/b]

---

<<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?

[neufer]

---

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.

Does that mean the moon Trumps the earth?

[heehaw]

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

[MarkBour]

(Nice simulated image, just above.)

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 :

• Surveyor 3 was the first lunar spacecraft to image such an eclipse http://www.alpo-astronomy.org/eclipse/o ... pter15.htm
• There is an image from the Japanese probe Kaguya that Phil Plait posted on his Bad Astronomy site:
  http://www.kaguya.jaxa.jp/image/communi ... 218_01.jpg
• Cassini sent a beautiful view of this -- for Saturn, not Earth: https://saturn.jpl.nasa.gov/resources/5918/
• The astronauts returning from the Moon in 1969 (particularly Apollo 12 astronaut Alan Bean reported on it). https://science.nasa.gov/science-news/s ... nareclipse

Philosophically speaking, we witness a Solar eclipse by the Earth every night, right here at home.

[BillBixby]

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?

[Chris Peterson]

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

[BillBixby]

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]

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.

[Boomer12k]

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

:---[===] *

[Guest]

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.

[neufer]

---

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.