Could Apollo astronauts see city lights from the moon?How dark is the side of the Moon in shadow as compared to the side facing the Sun?How did astronauts traverse from module to module in the Apollo craft?Why did NASA send two astronauts to the moon instead of one?Why were the “perfectly functioning” seismometers placed by Apollo 12, 14, 15 and 16 astronauts all shut off in 1977?Could a radio telescope orbit Earth-Moon L2 so that it is in the Moon's radio shadow?How do we know the Apollo Moon landings are real?Did the Apollo missions use the Earth's magnetotail to lessen cosmic radiation?What was the temperature of the Apollo 11 moon landing zone?
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Could Apollo astronauts see city lights from the moon?
How dark is the side of the Moon in shadow as compared to the side facing the Sun?How did astronauts traverse from module to module in the Apollo craft?Why did NASA send two astronauts to the moon instead of one?Why were the “perfectly functioning” seismometers placed by Apollo 12, 14, 15 and 16 astronauts all shut off in 1977?Could a radio telescope orbit Earth-Moon L2 so that it is in the Moon's radio shadow?How do we know the Apollo Moon landings are real?Did the Apollo missions use the Earth's magnetotail to lessen cosmic radiation?What was the temperature of the Apollo 11 moon landing zone?
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$begingroup$
You can see city lights from orbit on the night side of Earth. A lot of science fiction (yes, sorry...it's one of those questions) has dialogue such as "on a clear night you can see XYZ city on the moon."
Obviously, we have no cities on the moon, but we do have cities on the Earth. Did the Apollo astronauts see them from the moon or at least Lunar orbit?
the-moon apollo-program earth-observation
edited 5 hours ago
Camille Goudeseune
1,9369 silver badges26 bronze badges
asked 8 hours ago
Michael StachowskyMichael Stachowsky
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$endgroup$
|
show 3 more comments
$begingroup$
You can see city lights from orbit on the night side of Earth. A lot of science fiction (yes, sorry...it's one of those questions) has dialogue such as "on a clear night you can see XYZ city on the moon."
Obviously, we have no cities on the moon, but we do have cities on the Earth. Did the Apollo astronauts see them from the moon or at least Lunar orbit?
the-moon apollo-program earth-observation
edited 5 hours ago
Camille Goudeseune
1,9369 silver badges26 bronze badges
asked 8 hours ago
Michael StachowskyMichael Stachowsky
2,5223 silver badges15 bronze badges
$endgroup$
1
$begingroup$
Interesting, all the pictures I remember show a daylight or half Earth. I wonder if there was ever even a dark Earth while astronauts were on the moon.
$endgroup$
– Organic Marble
8 hours ago
2
$begingroup$
The Apollo missions landed during a lunar day. They closed the IR and UV protecting visor of their helmets. So the astronaut eyes where not adapted to full sensiblity at night. They should have a view of the night side of Earth.
$endgroup$
– Uwe
8 hours ago
3
$begingroup$
On a "half Earth" it's going to be very difficult because the day side is so bright.
$endgroup$
– Organic Marble
8 hours ago
1
$begingroup$
@OrganicMarble I wasn't able to find anything in the transcripts with several different queries. It wasn't an exhaustive search, but if there were any obvious mention of city lights or lights on Earth I think I would have picked it up.
$endgroup$
– called2voyage♦
8 hours ago
4
$begingroup$
I'm leaning toward it not being possible during the Apollo missions, because if it was, I think we would have a famous picture of it. It is possible, as Organic said, that none of the missions encountered a dark Earth while on the lunar surface and if they had that they might have been able to see the city lights.
$endgroup$
– called2voyage♦
8 hours ago
|
show 3 more comments
$begingroup$
You can see city lights from orbit on the night side of Earth. A lot of science fiction (yes, sorry...it's one of those questions) has dialogue such as "on a clear night you can see XYZ city on the moon."
Obviously, we have no cities on the moon, but we do have cities on the Earth. Did the Apollo astronauts see them from the moon or at least Lunar orbit?
the-moon apollo-program earth-observation
edited 5 hours ago
Camille Goudeseune
1,9369 silver badges26 bronze badges
asked 8 hours ago
Michael StachowskyMichael Stachowsky
2,5223 silver badges15 bronze badges
$endgroup$
You can see city lights from orbit on the night side of Earth. A lot of science fiction (yes, sorry...it's one of those questions) has dialogue such as "on a clear night you can see XYZ city on the moon."
Obviously, we have no cities on the moon, but we do have cities on the Earth. Did the Apollo astronauts see them from the moon or at least Lunar orbit?
the-moon apollo-program earth-observation
the-moon apollo-program earth-observation
edited 5 hours ago
Camille Goudeseune
1,9369 silver badges26 bronze badges
asked 8 hours ago
Michael StachowskyMichael Stachowsky
2,5223 silver badges15 bronze badges
edited 5 hours ago
Camille Goudeseune
1,9369 silver badges26 bronze badges
asked 8 hours ago
Michael StachowskyMichael Stachowsky
2,5223 silver badges15 bronze badges
edited 5 hours ago
Camille Goudeseune
1,9369 silver badges26 bronze badges
edited 5 hours ago
Camille Goudeseune
1,9369 silver badges26 bronze badges
edited 5 hours ago
Camille Goudeseune
1,9369 silver badges26 bronze badges
1,9369 silver badges26 bronze badges
asked 8 hours ago
Michael StachowskyMichael Stachowsky
2,5223 silver badges15 bronze badges
asked 8 hours ago
Michael StachowskyMichael Stachowsky
2,5223 silver badges15 bronze badges
asked 8 hours ago
Michael StachowskyMichael Stachowsky
2,5223 silver badges15 bronze badges
2,5223 silver badges15 bronze badges
1
$begingroup$
Interesting, all the pictures I remember show a daylight or half Earth. I wonder if there was ever even a dark Earth while astronauts were on the moon.
$endgroup$
– Organic Marble
8 hours ago
2
$begingroup$
The Apollo missions landed during a lunar day. They closed the IR and UV protecting visor of their helmets. So the astronaut eyes where not adapted to full sensiblity at night. They should have a view of the night side of Earth.
$endgroup$
– Uwe
8 hours ago
3
$begingroup$
On a "half Earth" it's going to be very difficult because the day side is so bright.
$endgroup$
– Organic Marble
8 hours ago
1
$begingroup$
@OrganicMarble I wasn't able to find anything in the transcripts with several different queries. It wasn't an exhaustive search, but if there were any obvious mention of city lights or lights on Earth I think I would have picked it up.
$endgroup$
– called2voyage♦
8 hours ago
4
$begingroup$
I'm leaning toward it not being possible during the Apollo missions, because if it was, I think we would have a famous picture of it. It is possible, as Organic said, that none of the missions encountered a dark Earth while on the lunar surface and if they had that they might have been able to see the city lights.
$endgroup$
– called2voyage♦
8 hours ago
|
show 3 more comments
1
$begingroup$
Interesting, all the pictures I remember show a daylight or half Earth. I wonder if there was ever even a dark Earth while astronauts were on the moon.
$endgroup$
– Organic Marble
8 hours ago
2
$begingroup$
The Apollo missions landed during a lunar day. They closed the IR and UV protecting visor of their helmets. So the astronaut eyes where not adapted to full sensiblity at night. They should have a view of the night side of Earth.
$endgroup$
– Uwe
8 hours ago
3
$begingroup$
On a "half Earth" it's going to be very difficult because the day side is so bright.
$endgroup$
– Organic Marble
8 hours ago
1
$begingroup$
@OrganicMarble I wasn't able to find anything in the transcripts with several different queries. It wasn't an exhaustive search, but if there were any obvious mention of city lights or lights on Earth I think I would have picked it up.
$endgroup$
– called2voyage♦
8 hours ago
4
$begingroup$
I'm leaning toward it not being possible during the Apollo missions, because if it was, I think we would have a famous picture of it. It is possible, as Organic said, that none of the missions encountered a dark Earth while on the lunar surface and if they had that they might have been able to see the city lights.
$endgroup$
– called2voyage♦
8 hours ago
1
1
$begingroup$
Interesting, all the pictures I remember show a daylight or half Earth. I wonder if there was ever even a dark Earth while astronauts were on the moon.
$endgroup$
– Organic Marble
8 hours ago
$begingroup$
Interesting, all the pictures I remember show a daylight or half Earth. I wonder if there was ever even a dark Earth while astronauts were on the moon.
$endgroup$
– Organic Marble
8 hours ago
2
2
$begingroup$
The Apollo missions landed during a lunar day. They closed the IR and UV protecting visor of their helmets. So the astronaut eyes where not adapted to full sensiblity at night. They should have a view of the night side of Earth.
$endgroup$
– Uwe
8 hours ago
$begingroup$
The Apollo missions landed during a lunar day. They closed the IR and UV protecting visor of their helmets. So the astronaut eyes where not adapted to full sensiblity at night. They should have a view of the night side of Earth.
$endgroup$
– Uwe
8 hours ago
3
3
$begingroup$
On a "half Earth" it's going to be very difficult because the day side is so bright.
$endgroup$
– Organic Marble
8 hours ago
$begingroup$
On a "half Earth" it's going to be very difficult because the day side is so bright.
$endgroup$
– Organic Marble
8 hours ago
1
1
$begingroup$
@OrganicMarble I wasn't able to find anything in the transcripts with several different queries. It wasn't an exhaustive search, but if there were any obvious mention of city lights or lights on Earth I think I would have picked it up.
$endgroup$
– called2voyage♦
8 hours ago
$begingroup$
@OrganicMarble I wasn't able to find anything in the transcripts with several different queries. It wasn't an exhaustive search, but if there were any obvious mention of city lights or lights on Earth I think I would have picked it up.
$endgroup$
– called2voyage♦
8 hours ago
4
4
$begingroup$
I'm leaning toward it not being possible during the Apollo missions, because if it was, I think we would have a famous picture of it. It is possible, as Organic said, that none of the missions encountered a dark Earth while on the lunar surface and if they had that they might have been able to see the city lights.
$endgroup$
– called2voyage♦
8 hours ago
$begingroup$
I'm leaning toward it not being possible during the Apollo missions, because if it was, I think we would have a famous picture of it. It is possible, as Organic said, that none of the missions encountered a dark Earth while on the lunar surface and if they had that they might have been able to see the city lights.
$endgroup$
– called2voyage♦
8 hours ago
|
show 3 more comments
2 Answers
2
active
oldest
votes
$begingroup$
Beyond LEO, once you're a few Earth radii away, far enough to see the entire planet, its nightside is a featureless black, at least to conventional cameras, in every one of the dozens of photos at http://www.planetary.org/explore/space-topics/earth/pics-of-earth-by-planetary-spacecraft.html, even the ones that show Earth as only a slim crescent. And these cameras don't suffer from human eyes' lack of dark adaptation because of the bright dayside.
Handwaving and possibly erroneous math: The nighttime-glowing part of Chicago is about 400 km2, the same as a disc of radius 11 km. Compare nighttime Chicago to a 22 km diameter asteroid with a whoppingly generous albedo of 0.05. Then its absolute magnitude is about 12 (its magnitude seen from 1 AU away, in that table). Seen from 239,000 miles away instead of 93,000,000, 390 times closer, it's $390 times 390 = 150000 = 2.5^13$ times brighter, so its apparent magnitude is $12-13 = -1$, as bright as Sirius.
My estimate is likely incorrect of what a 20 km asteroid's albedo must be to match nighttime Chicaglow (what terrestrial Midwestern astronomers nickname its light pollution). But at least, seen from the moon, Chicago is no brighter than Sirius, and probably closer to magnitude 3 or 4, barely visible even without a distracting magnitude -15 Earth visible.
answered 5 hours ago
Camille GoudeseuneCamille Goudeseune
1,9369 silver badges26 bronze badges
$endgroup$
$begingroup$
"... its nightside is a featureless black, at least to conventional cameras..." which don't have anywhere near the dynamic range as human vision. Single exposures by conventional spacecraft digital cameras with settings to keep the bright side from being overexposed will have the night side in the noise. That doesn't mean at all that a human eye couldn't perceive city lights in the night side. This is why digital photography has High-dynamic-range imaging.
$endgroup$
– uhoh
3 hours ago
$begingroup$
It would be much more convincing to find an Apollo era image using photographic emulsion with it's better dynamic range.
$endgroup$
– uhoh
3 hours ago
$begingroup$
Veering into chat: the human eye's overall dynamic range is mostly due to irising. At a fixed aperture (for the astronauts, set by bright Earth dayside), it's still better than film or CCD, but not nearly so much.
$endgroup$
– Camille Goudeseune
37 mins ago
1
$begingroup$
But that doesn't mean that without irising it isn't still better than the ADC dynamic range used in the spacecraft imagers, which use exposure time to accomplish a similar thing that irising provides in humans. Also, an astronaut can simply cover the bright part of the Earth with a glove. I'm going to go off this weekend and do some reading about human vision's dynamic range within a visual field. To be continued...
$endgroup$
– uhoh
24 mins ago
add a comment
|
$begingroup$
An independent calculation. From the ISS, Venus is as bright as the city of Valencia at night. (Other ISS views of Venus had places on Earth that I didn't recognize.) Valencia's metropolis has about 2M people.
In the 1970's Earth's biggest megacity, greater Tokyo, had about 23M people. 11.5 times as many, so 11.5 times brighter. (Maybe less because lighting was less efficient then, maybe more because we didn't fuss so much about light pollution then.)
ISS is 400 km up, so about 800 km from Valencia in that image.
The moon is 385,000 km away, 480 times farther.
So from the moon, 1970's Tokyo was $11.5 / (480 times 480) = 1/20000$ times as bright as Venus.
Venus has apparent magnitude $-4$.
$20000 = 2.5^10.8$.
So from the moon, Tokyo had magnitude $-4 + 10.8 = 6.8.$
Under optimum conditions, stars of magnitude 6.5 are the threshold of visibility with the naked eye.
Thus, with the magnitude -15 dayside earth and the magnitude -26 sun dazzling the astronauts (a factor that swamps all the other estimating errors in this answer), even the brightest nightside city was too dim for them to see.
Their only chance to see city lights would have been during a solar eclipse and even then, still only magnitude 6.8, if Tokyo was facing them, without clouds.
answered 4 hours ago
Camille GoudeseuneCamille Goudeseune
1,9369 silver badges26 bronze badges
$endgroup$
$begingroup$
Two problems: 1) that image is full of saturated pixels so it's impossible to be quantitative, 2) the city's bright pixels are spread over perhaps 100x or 1000x more area than Venus, so it can be arguable that the city is 100 or 1000 times brighter than Venus. A factor of 100 is 5 magnitudes for example, so your magnitude 6.8 could be +1.8 or -0.7 magnitude. It's also important to remember that at 480 times farther away, Tokyo would also be close to an unresolved point (nearly star-like), rather than an extended area. I don't think your analysis is currently valid.
$endgroup$
– uhoh
3 hours ago
add a comment
|
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2 Answers
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2 Answers
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$begingroup$
Beyond LEO, once you're a few Earth radii away, far enough to see the entire planet, its nightside is a featureless black, at least to conventional cameras, in every one of the dozens of photos at http://www.planetary.org/explore/space-topics/earth/pics-of-earth-by-planetary-spacecraft.html, even the ones that show Earth as only a slim crescent. And these cameras don't suffer from human eyes' lack of dark adaptation because of the bright dayside.
Handwaving and possibly erroneous math: The nighttime-glowing part of Chicago is about 400 km2, the same as a disc of radius 11 km. Compare nighttime Chicago to a 22 km diameter asteroid with a whoppingly generous albedo of 0.05. Then its absolute magnitude is about 12 (its magnitude seen from 1 AU away, in that table). Seen from 239,000 miles away instead of 93,000,000, 390 times closer, it's $390 times 390 = 150000 = 2.5^13$ times brighter, so its apparent magnitude is $12-13 = -1$, as bright as Sirius.
My estimate is likely incorrect of what a 20 km asteroid's albedo must be to match nighttime Chicaglow (what terrestrial Midwestern astronomers nickname its light pollution). But at least, seen from the moon, Chicago is no brighter than Sirius, and probably closer to magnitude 3 or 4, barely visible even without a distracting magnitude -15 Earth visible.
answered 5 hours ago
Camille GoudeseuneCamille Goudeseune
1,9369 silver badges26 bronze badges
$endgroup$
$begingroup$
"... its nightside is a featureless black, at least to conventional cameras..." which don't have anywhere near the dynamic range as human vision. Single exposures by conventional spacecraft digital cameras with settings to keep the bright side from being overexposed will have the night side in the noise. That doesn't mean at all that a human eye couldn't perceive city lights in the night side. This is why digital photography has High-dynamic-range imaging.
$endgroup$
– uhoh
3 hours ago
$begingroup$
It would be much more convincing to find an Apollo era image using photographic emulsion with it's better dynamic range.
$endgroup$
– uhoh
3 hours ago
$begingroup$
Veering into chat: the human eye's overall dynamic range is mostly due to irising. At a fixed aperture (for the astronauts, set by bright Earth dayside), it's still better than film or CCD, but not nearly so much.
$endgroup$
– Camille Goudeseune
37 mins ago
1
$begingroup$
But that doesn't mean that without irising it isn't still better than the ADC dynamic range used in the spacecraft imagers, which use exposure time to accomplish a similar thing that irising provides in humans. Also, an astronaut can simply cover the bright part of the Earth with a glove. I'm going to go off this weekend and do some reading about human vision's dynamic range within a visual field. To be continued...
$endgroup$
– uhoh
24 mins ago
add a comment
|
$begingroup$
Beyond LEO, once you're a few Earth radii away, far enough to see the entire planet, its nightside is a featureless black, at least to conventional cameras, in every one of the dozens of photos at http://www.planetary.org/explore/space-topics/earth/pics-of-earth-by-planetary-spacecraft.html, even the ones that show Earth as only a slim crescent. And these cameras don't suffer from human eyes' lack of dark adaptation because of the bright dayside.
Handwaving and possibly erroneous math: The nighttime-glowing part of Chicago is about 400 km2, the same as a disc of radius 11 km. Compare nighttime Chicago to a 22 km diameter asteroid with a whoppingly generous albedo of 0.05. Then its absolute magnitude is about 12 (its magnitude seen from 1 AU away, in that table). Seen from 239,000 miles away instead of 93,000,000, 390 times closer, it's $390 times 390 = 150000 = 2.5^13$ times brighter, so its apparent magnitude is $12-13 = -1$, as bright as Sirius.
My estimate is likely incorrect of what a 20 km asteroid's albedo must be to match nighttime Chicaglow (what terrestrial Midwestern astronomers nickname its light pollution). But at least, seen from the moon, Chicago is no brighter than Sirius, and probably closer to magnitude 3 or 4, barely visible even without a distracting magnitude -15 Earth visible.
answered 5 hours ago
Camille GoudeseuneCamille Goudeseune
1,9369 silver badges26 bronze badges
$endgroup$
$begingroup$
"... its nightside is a featureless black, at least to conventional cameras..." which don't have anywhere near the dynamic range as human vision. Single exposures by conventional spacecraft digital cameras with settings to keep the bright side from being overexposed will have the night side in the noise. That doesn't mean at all that a human eye couldn't perceive city lights in the night side. This is why digital photography has High-dynamic-range imaging.
$endgroup$
– uhoh
3 hours ago
$begingroup$
It would be much more convincing to find an Apollo era image using photographic emulsion with it's better dynamic range.
$endgroup$
– uhoh
3 hours ago
$begingroup$
Veering into chat: the human eye's overall dynamic range is mostly due to irising. At a fixed aperture (for the astronauts, set by bright Earth dayside), it's still better than film or CCD, but not nearly so much.
$endgroup$
– Camille Goudeseune
37 mins ago
1
$begingroup$
But that doesn't mean that without irising it isn't still better than the ADC dynamic range used in the spacecraft imagers, which use exposure time to accomplish a similar thing that irising provides in humans. Also, an astronaut can simply cover the bright part of the Earth with a glove. I'm going to go off this weekend and do some reading about human vision's dynamic range within a visual field. To be continued...
$endgroup$
– uhoh
24 mins ago
add a comment
|
$begingroup$
Beyond LEO, once you're a few Earth radii away, far enough to see the entire planet, its nightside is a featureless black, at least to conventional cameras, in every one of the dozens of photos at http://www.planetary.org/explore/space-topics/earth/pics-of-earth-by-planetary-spacecraft.html, even the ones that show Earth as only a slim crescent. And these cameras don't suffer from human eyes' lack of dark adaptation because of the bright dayside.
Handwaving and possibly erroneous math: The nighttime-glowing part of Chicago is about 400 km2, the same as a disc of radius 11 km. Compare nighttime Chicago to a 22 km diameter asteroid with a whoppingly generous albedo of 0.05. Then its absolute magnitude is about 12 (its magnitude seen from 1 AU away, in that table). Seen from 239,000 miles away instead of 93,000,000, 390 times closer, it's $390 times 390 = 150000 = 2.5^13$ times brighter, so its apparent magnitude is $12-13 = -1$, as bright as Sirius.
My estimate is likely incorrect of what a 20 km asteroid's albedo must be to match nighttime Chicaglow (what terrestrial Midwestern astronomers nickname its light pollution). But at least, seen from the moon, Chicago is no brighter than Sirius, and probably closer to magnitude 3 or 4, barely visible even without a distracting magnitude -15 Earth visible.
answered 5 hours ago
Camille GoudeseuneCamille Goudeseune
1,9369 silver badges26 bronze badges
$endgroup$
Beyond LEO, once you're a few Earth radii away, far enough to see the entire planet, its nightside is a featureless black, at least to conventional cameras, in every one of the dozens of photos at http://www.planetary.org/explore/space-topics/earth/pics-of-earth-by-planetary-spacecraft.html, even the ones that show Earth as only a slim crescent. And these cameras don't suffer from human eyes' lack of dark adaptation because of the bright dayside.
Handwaving and possibly erroneous math: The nighttime-glowing part of Chicago is about 400 km2, the same as a disc of radius 11 km. Compare nighttime Chicago to a 22 km diameter asteroid with a whoppingly generous albedo of 0.05. Then its absolute magnitude is about 12 (its magnitude seen from 1 AU away, in that table). Seen from 239,000 miles away instead of 93,000,000, 390 times closer, it's $390 times 390 = 150000 = 2.5^13$ times brighter, so its apparent magnitude is $12-13 = -1$, as bright as Sirius.
My estimate is likely incorrect of what a 20 km asteroid's albedo must be to match nighttime Chicaglow (what terrestrial Midwestern astronomers nickname its light pollution). But at least, seen from the moon, Chicago is no brighter than Sirius, and probably closer to magnitude 3 or 4, barely visible even without a distracting magnitude -15 Earth visible.
answered 5 hours ago
Camille GoudeseuneCamille Goudeseune
1,9369 silver badges26 bronze badges
answered 5 hours ago
Camille GoudeseuneCamille Goudeseune
1,9369 silver badges26 bronze badges
answered 5 hours ago
Camille GoudeseuneCamille Goudeseune
1,9369 silver badges26 bronze badges
answered 5 hours ago
Camille GoudeseuneCamille Goudeseune
1,9369 silver badges26 bronze badges
1,9369 silver badges26 bronze badges
$begingroup$
"... its nightside is a featureless black, at least to conventional cameras..." which don't have anywhere near the dynamic range as human vision. Single exposures by conventional spacecraft digital cameras with settings to keep the bright side from being overexposed will have the night side in the noise. That doesn't mean at all that a human eye couldn't perceive city lights in the night side. This is why digital photography has High-dynamic-range imaging.
$endgroup$
– uhoh
3 hours ago
$begingroup$
It would be much more convincing to find an Apollo era image using photographic emulsion with it's better dynamic range.
$endgroup$
– uhoh
3 hours ago
$begingroup$
Veering into chat: the human eye's overall dynamic range is mostly due to irising. At a fixed aperture (for the astronauts, set by bright Earth dayside), it's still better than film or CCD, but not nearly so much.
$endgroup$
– Camille Goudeseune
37 mins ago
1
$begingroup$
But that doesn't mean that without irising it isn't still better than the ADC dynamic range used in the spacecraft imagers, which use exposure time to accomplish a similar thing that irising provides in humans. Also, an astronaut can simply cover the bright part of the Earth with a glove. I'm going to go off this weekend and do some reading about human vision's dynamic range within a visual field. To be continued...
$endgroup$
– uhoh
24 mins ago
add a comment
|
$begingroup$
"... its nightside is a featureless black, at least to conventional cameras..." which don't have anywhere near the dynamic range as human vision. Single exposures by conventional spacecraft digital cameras with settings to keep the bright side from being overexposed will have the night side in the noise. That doesn't mean at all that a human eye couldn't perceive city lights in the night side. This is why digital photography has High-dynamic-range imaging.
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– uhoh
3 hours ago
$begingroup$
It would be much more convincing to find an Apollo era image using photographic emulsion with it's better dynamic range.
$endgroup$
– uhoh
3 hours ago
$begingroup$
Veering into chat: the human eye's overall dynamic range is mostly due to irising. At a fixed aperture (for the astronauts, set by bright Earth dayside), it's still better than film or CCD, but not nearly so much.
$endgroup$
– Camille Goudeseune
37 mins ago
1
$begingroup$
But that doesn't mean that without irising it isn't still better than the ADC dynamic range used in the spacecraft imagers, which use exposure time to accomplish a similar thing that irising provides in humans. Also, an astronaut can simply cover the bright part of the Earth with a glove. I'm going to go off this weekend and do some reading about human vision's dynamic range within a visual field. To be continued...
$endgroup$
– uhoh
24 mins ago
$begingroup$
"... its nightside is a featureless black, at least to conventional cameras..." which don't have anywhere near the dynamic range as human vision. Single exposures by conventional spacecraft digital cameras with settings to keep the bright side from being overexposed will have the night side in the noise. That doesn't mean at all that a human eye couldn't perceive city lights in the night side. This is why digital photography has High-dynamic-range imaging.
$endgroup$
– uhoh
3 hours ago
$begingroup$
"... its nightside is a featureless black, at least to conventional cameras..." which don't have anywhere near the dynamic range as human vision. Single exposures by conventional spacecraft digital cameras with settings to keep the bright side from being overexposed will have the night side in the noise. That doesn't mean at all that a human eye couldn't perceive city lights in the night side. This is why digital photography has High-dynamic-range imaging.
$endgroup$
– uhoh
3 hours ago
$begingroup$
It would be much more convincing to find an Apollo era image using photographic emulsion with it's better dynamic range.
$endgroup$
– uhoh
3 hours ago
$begingroup$
It would be much more convincing to find an Apollo era image using photographic emulsion with it's better dynamic range.
$endgroup$
– uhoh
3 hours ago
$begingroup$
Veering into chat: the human eye's overall dynamic range is mostly due to irising. At a fixed aperture (for the astronauts, set by bright Earth dayside), it's still better than film or CCD, but not nearly so much.
$endgroup$
– Camille Goudeseune
37 mins ago
$begingroup$
Veering into chat: the human eye's overall dynamic range is mostly due to irising. At a fixed aperture (for the astronauts, set by bright Earth dayside), it's still better than film or CCD, but not nearly so much.
$endgroup$
– Camille Goudeseune
37 mins ago
1
1
$begingroup$
But that doesn't mean that without irising it isn't still better than the ADC dynamic range used in the spacecraft imagers, which use exposure time to accomplish a similar thing that irising provides in humans. Also, an astronaut can simply cover the bright part of the Earth with a glove. I'm going to go off this weekend and do some reading about human vision's dynamic range within a visual field. To be continued...
$endgroup$
– uhoh
24 mins ago
$begingroup$
But that doesn't mean that without irising it isn't still better than the ADC dynamic range used in the spacecraft imagers, which use exposure time to accomplish a similar thing that irising provides in humans. Also, an astronaut can simply cover the bright part of the Earth with a glove. I'm going to go off this weekend and do some reading about human vision's dynamic range within a visual field. To be continued...
$endgroup$
– uhoh
24 mins ago
add a comment
|
$begingroup$
An independent calculation. From the ISS, Venus is as bright as the city of Valencia at night. (Other ISS views of Venus had places on Earth that I didn't recognize.) Valencia's metropolis has about 2M people.
In the 1970's Earth's biggest megacity, greater Tokyo, had about 23M people. 11.5 times as many, so 11.5 times brighter. (Maybe less because lighting was less efficient then, maybe more because we didn't fuss so much about light pollution then.)
ISS is 400 km up, so about 800 km from Valencia in that image.
The moon is 385,000 km away, 480 times farther.
So from the moon, 1970's Tokyo was $11.5 / (480 times 480) = 1/20000$ times as bright as Venus.
Venus has apparent magnitude $-4$.
$20000 = 2.5^10.8$.
So from the moon, Tokyo had magnitude $-4 + 10.8 = 6.8.$
Under optimum conditions, stars of magnitude 6.5 are the threshold of visibility with the naked eye.
Thus, with the magnitude -15 dayside earth and the magnitude -26 sun dazzling the astronauts (a factor that swamps all the other estimating errors in this answer), even the brightest nightside city was too dim for them to see.
Their only chance to see city lights would have been during a solar eclipse and even then, still only magnitude 6.8, if Tokyo was facing them, without clouds.
answered 4 hours ago
Camille GoudeseuneCamille Goudeseune
1,9369 silver badges26 bronze badges
$endgroup$
$begingroup$
Two problems: 1) that image is full of saturated pixels so it's impossible to be quantitative, 2) the city's bright pixels are spread over perhaps 100x or 1000x more area than Venus, so it can be arguable that the city is 100 or 1000 times brighter than Venus. A factor of 100 is 5 magnitudes for example, so your magnitude 6.8 could be +1.8 or -0.7 magnitude. It's also important to remember that at 480 times farther away, Tokyo would also be close to an unresolved point (nearly star-like), rather than an extended area. I don't think your analysis is currently valid.
$endgroup$
– uhoh
3 hours ago
add a comment
|
$begingroup$
An independent calculation. From the ISS, Venus is as bright as the city of Valencia at night. (Other ISS views of Venus had places on Earth that I didn't recognize.) Valencia's metropolis has about 2M people.
In the 1970's Earth's biggest megacity, greater Tokyo, had about 23M people. 11.5 times as many, so 11.5 times brighter. (Maybe less because lighting was less efficient then, maybe more because we didn't fuss so much about light pollution then.)
ISS is 400 km up, so about 800 km from Valencia in that image.
The moon is 385,000 km away, 480 times farther.
So from the moon, 1970's Tokyo was $11.5 / (480 times 480) = 1/20000$ times as bright as Venus.
Venus has apparent magnitude $-4$.
$20000 = 2.5^10.8$.
So from the moon, Tokyo had magnitude $-4 + 10.8 = 6.8.$
Under optimum conditions, stars of magnitude 6.5 are the threshold of visibility with the naked eye.
Thus, with the magnitude -15 dayside earth and the magnitude -26 sun dazzling the astronauts (a factor that swamps all the other estimating errors in this answer), even the brightest nightside city was too dim for them to see.
Their only chance to see city lights would have been during a solar eclipse and even then, still only magnitude 6.8, if Tokyo was facing them, without clouds.
answered 4 hours ago
Camille GoudeseuneCamille Goudeseune
1,9369 silver badges26 bronze badges
$endgroup$
$begingroup$
Two problems: 1) that image is full of saturated pixels so it's impossible to be quantitative, 2) the city's bright pixels are spread over perhaps 100x or 1000x more area than Venus, so it can be arguable that the city is 100 or 1000 times brighter than Venus. A factor of 100 is 5 magnitudes for example, so your magnitude 6.8 could be +1.8 or -0.7 magnitude. It's also important to remember that at 480 times farther away, Tokyo would also be close to an unresolved point (nearly star-like), rather than an extended area. I don't think your analysis is currently valid.
$endgroup$
– uhoh
3 hours ago
add a comment
|
$begingroup$
An independent calculation. From the ISS, Venus is as bright as the city of Valencia at night. (Other ISS views of Venus had places on Earth that I didn't recognize.) Valencia's metropolis has about 2M people.
In the 1970's Earth's biggest megacity, greater Tokyo, had about 23M people. 11.5 times as many, so 11.5 times brighter. (Maybe less because lighting was less efficient then, maybe more because we didn't fuss so much about light pollution then.)
ISS is 400 km up, so about 800 km from Valencia in that image.
The moon is 385,000 km away, 480 times farther.
So from the moon, 1970's Tokyo was $11.5 / (480 times 480) = 1/20000$ times as bright as Venus.
Venus has apparent magnitude $-4$.
$20000 = 2.5^10.8$.
So from the moon, Tokyo had magnitude $-4 + 10.8 = 6.8.$
Under optimum conditions, stars of magnitude 6.5 are the threshold of visibility with the naked eye.
Thus, with the magnitude -15 dayside earth and the magnitude -26 sun dazzling the astronauts (a factor that swamps all the other estimating errors in this answer), even the brightest nightside city was too dim for them to see.
Their only chance to see city lights would have been during a solar eclipse and even then, still only magnitude 6.8, if Tokyo was facing them, without clouds.
answered 4 hours ago
Camille GoudeseuneCamille Goudeseune
1,9369 silver badges26 bronze badges
$endgroup$
An independent calculation. From the ISS, Venus is as bright as the city of Valencia at night. (Other ISS views of Venus had places on Earth that I didn't recognize.) Valencia's metropolis has about 2M people.
In the 1970's Earth's biggest megacity, greater Tokyo, had about 23M people. 11.5 times as many, so 11.5 times brighter. (Maybe less because lighting was less efficient then, maybe more because we didn't fuss so much about light pollution then.)
ISS is 400 km up, so about 800 km from Valencia in that image.
The moon is 385,000 km away, 480 times farther.
So from the moon, 1970's Tokyo was $11.5 / (480 times 480) = 1/20000$ times as bright as Venus.
Venus has apparent magnitude $-4$.
$20000 = 2.5^10.8$.
So from the moon, Tokyo had magnitude $-4 + 10.8 = 6.8.$
Under optimum conditions, stars of magnitude 6.5 are the threshold of visibility with the naked eye.
Thus, with the magnitude -15 dayside earth and the magnitude -26 sun dazzling the astronauts (a factor that swamps all the other estimating errors in this answer), even the brightest nightside city was too dim for them to see.
Their only chance to see city lights would have been during a solar eclipse and even then, still only magnitude 6.8, if Tokyo was facing them, without clouds.
answered 4 hours ago
Camille GoudeseuneCamille Goudeseune
1,9369 silver badges26 bronze badges
edited 4 hours ago
answered 4 hours ago
Camille GoudeseuneCamille Goudeseune
1,9369 silver badges26 bronze badges
answered 4 hours ago
Camille GoudeseuneCamille Goudeseune
1,9369 silver badges26 bronze badges
answered 4 hours ago
Camille GoudeseuneCamille Goudeseune
1,9369 silver badges26 bronze badges
1,9369 silver badges26 bronze badges
$begingroup$
Two problems: 1) that image is full of saturated pixels so it's impossible to be quantitative, 2) the city's bright pixels are spread over perhaps 100x or 1000x more area than Venus, so it can be arguable that the city is 100 or 1000 times brighter than Venus. A factor of 100 is 5 magnitudes for example, so your magnitude 6.8 could be +1.8 or -0.7 magnitude. It's also important to remember that at 480 times farther away, Tokyo would also be close to an unresolved point (nearly star-like), rather than an extended area. I don't think your analysis is currently valid.
$endgroup$
– uhoh
3 hours ago
add a comment
|
$begingroup$
Two problems: 1) that image is full of saturated pixels so it's impossible to be quantitative, 2) the city's bright pixels are spread over perhaps 100x or 1000x more area than Venus, so it can be arguable that the city is 100 or 1000 times brighter than Venus. A factor of 100 is 5 magnitudes for example, so your magnitude 6.8 could be +1.8 or -0.7 magnitude. It's also important to remember that at 480 times farther away, Tokyo would also be close to an unresolved point (nearly star-like), rather than an extended area. I don't think your analysis is currently valid.
$endgroup$
– uhoh
3 hours ago
$begingroup$
Two problems: 1) that image is full of saturated pixels so it's impossible to be quantitative, 2) the city's bright pixels are spread over perhaps 100x or 1000x more area than Venus, so it can be arguable that the city is 100 or 1000 times brighter than Venus. A factor of 100 is 5 magnitudes for example, so your magnitude 6.8 could be +1.8 or -0.7 magnitude. It's also important to remember that at 480 times farther away, Tokyo would also be close to an unresolved point (nearly star-like), rather than an extended area. I don't think your analysis is currently valid.
$endgroup$
– uhoh
3 hours ago
$begingroup$
Two problems: 1) that image is full of saturated pixels so it's impossible to be quantitative, 2) the city's bright pixels are spread over perhaps 100x or 1000x more area than Venus, so it can be arguable that the city is 100 or 1000 times brighter than Venus. A factor of 100 is 5 magnitudes for example, so your magnitude 6.8 could be +1.8 or -0.7 magnitude. It's also important to remember that at 480 times farther away, Tokyo would also be close to an unresolved point (nearly star-like), rather than an extended area. I don't think your analysis is currently valid.
$endgroup$
– uhoh
3 hours ago
add a comment
|
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$begingroup$
Interesting, all the pictures I remember show a daylight or half Earth. I wonder if there was ever even a dark Earth while astronauts were on the moon.
$endgroup$
– Organic Marble
8 hours ago
2
$begingroup$
The Apollo missions landed during a lunar day. They closed the IR and UV protecting visor of their helmets. So the astronaut eyes where not adapted to full sensiblity at night. They should have a view of the night side of Earth.
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– Uwe
8 hours ago
3
$begingroup$
On a "half Earth" it's going to be very difficult because the day side is so bright.
$endgroup$
– Organic Marble
8 hours ago
1
$begingroup$
@OrganicMarble I wasn't able to find anything in the transcripts with several different queries. It wasn't an exhaustive search, but if there were any obvious mention of city lights or lights on Earth I think I would have picked it up.
$endgroup$
– called2voyage♦
8 hours ago
4
$begingroup$
I'm leaning toward it not being possible during the Apollo missions, because if it was, I think we would have a famous picture of it. It is possible, as Organic said, that none of the missions encountered a dark Earth while on the lunar surface and if they had that they might have been able to see the city lights.
$endgroup$
– called2voyage♦
8 hours ago