APOD: Apollo 17: The Crescent Earth (2023 May 13)

[APOD Robot]

Apollo 17: The Crescent Earth

Explanation: Our fair planet sports a curved, sunlit crescent against the black backdrop of space in this stunning photograph. From the unfamiliar perspective, the Earth is small and, like a telescopic image of a distant planet, the entire horizon is completely within the field of view. Enjoyed by crews on board the International Space Station, only much closer views of the planet are possible from low Earth orbit. Orbiting the planet once every 90 minutes, a spectacle of clouds, oceans, and continents scrolls beneath them with the partial arc of the planet's edge in the distance. But this digitally restored image presents a view so far only achieved by 24 humans, Apollo astronauts who traveled to the Moon and back again between 1968 and 1972. The original photograph, AS17-152-23420, was taken by the homeward bound crew of Apollo 17, on December 17, 1972. For now it is the last picture of Earth from this planetary perspective taken by human hands.

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[Rauf]

Does anyone know which part of the earth are we seeing in that sunlit crescent??
Or which side is north?

[orin stepanek]

Such beauty is the Earth when seen from near space!
I'd love to be on that flight to the moon!

[Chris Peterson]

But this digitally restored image presents a view so far only achieved by 24 humans, Apollo astronauts who traveled to the Moon and back again between 1968 and 1972.

In case it comes up - because it did the last time this image was run - there were 9 Apollo missions that rounded the Moon: 8, 10, 11, 12, 13, 14, 15, 16, and 17. So 9 x 3 = 27 sets of eyes on views like this. But three of the Apollo astronauts were on two of those missions, so only 24 people who have seen this first hand.

[johnnydeep]

I though the use of the phrase "entire horizon" in the text was somewhat odd...until I looked up the etymology!'

horizon (n.)
late 14c., orisoun, from Old French orizon (14c., Modern French horizon), earlier orizonte (13c.), from Latin horizontem (nominative horizon), from Greek horizon (kyklos) "bounding (circle)," from horizein "bound, limit, divide, separate," from horos "boundary, landmark, marking stones." The h- was restored in English 17c. in imitation of Latin. Old English used eaggemearc ("eye-mark") for "limit of view, horizon." The apparent horizon is distinguished from the celestial or astronomical horizon.

[De58te]

Does anyone know which part of the earth are we seeing in that sunlit crescent??
Or which side is north?

If I may offer an unscientific guess we should consider the calendar date. Apollo 17 lunar lander took off from the surface of the Moon on December 14. Then the command module rocketed to Earth starting early on December 17th. Now that date is really close to the Winter Solstice. And because the Earth tilts 23 degrees south then and the South Pole is actually in 24 hours daylight then we can figure that the largest crescent is in the south and Antarctica is likely that large white mass on the right. The North hemisphere is likely in the darker left side and we can assume that the polar North Pole is completely hidden in the darkness.

[Rauf]

But, maybe the south pole is actually near the left side. I mean if It was the summer solstice, the crescent would just move a little bit upper or lower on earth right? So just the fact that it's winter solstice wouldn't imply that the right side is the south, and I don't get what you mean the largest crescent..

[jks]

But this digitally restored image presents a view so far only achieved by 24 humans, Apollo astronauts who traveled to the Moon and back again between 1968 and 1972.

In case it comes up - because it did the last time this image was run - there were 9 Apollo missions that rounded the Moon: 8, 10, 11, 12, 13, 14, 15, 16, and 17. So 9 x 3 = 27 sets of eyes on views like this. But three of the Apollo astronauts were on two of those missions, so only 24 people who have seen this first hand.

Speaking of the last time this image was run, it was about 3 months after this black and white image from Apollo 14 appeared. I liked the color image of Earth so much that I cheated and used it in place of the b & w image of Earth from Apollo 14 (I used a simple image editor, likely paint). The "cheat" image is in my screen wallpaper rotation, along with the somewhat similar image in this APOD.

[bls0326]

Does anyone know which part of the earth are we seeing in that sunlit crescent??
Or which side is north?

According to info about the picture, it was taken on Dec. 17,1972 23:00 UTC. The Apollo 17 Timeline shows an astronaut doing a deep-space walk around that time. An article on the deep-space walk shows they were about 180,000 miles (300,000 km) from Earth. I used that data in this website https://fourmilab.ch/cgi-bin/Earth and adjusted the viewing latitude and longitude to get the day/night terminator to match the picture (approximately). Basically the dark area is nighttime in Europe, northern Africa, and portions of Asia. The city lights do not show up probably because of the camera and type of film being used at the time. The attachment is a comparison of the two pictures.

[Rauf]

Does anyone know which part of the earth are we seeing in that sunlit crescent??
Or which side is north?

According to info about the picture, it was taken on Dec. 17,1972 23:00 UTC. The Apollo 17 Timeline shows an astronaut doing a deep-space walk around that time. An article on the deep-space walk shows they were about 180,000 miles (300,000 km) from Earth. I used that data in this website https://fourmilab.ch/cgi-bin/Earth and adjusted the viewing latitude and longitude to get the day/night terminator to match the picture (approximately). Basically the dark area is nighttime in Europe, northern Africa, and portions of Asia. The city lights do not show up probably because of the camera and type of film being used at the time. The attachment is a comparison of the two pictures.

Thank you very much. So the portion of Earth we can see on the left is actually Canada.. still very hard to distinguish lands on this thin crescent specially with all the coulds blocking the view.