Eclipse

''We're getting a spectacular view at eclipse,'' said Dick Gordon as Apollo 12 approached Earth. ''We're using the Sun filter for the G&N optics, looking through, and it's unbelievable.'' It was 4 hours before splashdown and he was astonished at the celestial spectacle that was unfolding through the hatch window as Yankee Clipper began to enter the shadow, and the limb of Earth gradually ate away at the Sun. To protect his eyes from the glare, he was using a strong filter normally used in the sextant.

''It's not quite a straight line, but it's certainly a large, large disk right now. Looks quite a bit different than when you see the Moon eclipse the Sun.'' The timing of this event had been known well in advance and the flight plan had it marked, but no one, not even the crew, had realised just what a feast for the eyes it would be. Now they were desperate to know what camera settings to use to try to capture the scene. Unfortunately, they had run out of colour film for their Hasselblad camera.

''Anybody down there know what we can set the camera at to use the Sun filter on it?'' asked Al Bean. ''To take a couple of shots of this eclipse right through it?'' ''Stand by and we'll check,'' replied Paul Weitz, final Capcom for the mission. ''They'd better hustle,'' said Bean, seeing how quickly things were changing. Still the glare of the Sun was drowning out the scene that was to unfold. ''You cannot see the Earth at all when you just shield your hand from the Sun and look where the Earth should be. It's not there at all.''

Soon the accelerating spacecraft had moved completely into Earth's shadow. ''Fantastic sight,'' called Bean. ''What we see now is that the Sun is almost completely eclipsed, and what it's done is illuminated the entire atmosphere all the way around the Earth.''

They were now about 60,000 kilometres from Earth and the planet was growing rapidly in their window, its limb glowing with the hues and tones of a 40,000-kilometre ring comprising the largest single sunset ever witnessed by humans. ''It really looks pretty. You can't see the Earth. It's black, just like space.''

Pete Conrad took up the commentary: "You can't see any features on it. All you can see is this sort of purple-blue, orange, some shades of violet, completely around the Earth. It has blues and pinks in it, but instead of being banded, it's segmented, which is very peculiar; I don't understand why. It may be the difference between over the landmasses and water or something.'' "Roger, Pete. Understand,'' replied Weitz.

"About a quarter of the Earth is pure blue, and then it becomes pink to about 20 degrees of arc; and then it turns back to blue again. And it's blue all the way around the bottom to where it turns pink again, and then it turns blue again.''

"It's a heck of a time to be without any 70-millimetre colour film, I'll tell you,'' bemoaned Bean, referring to the Hasselblad film. "But I know how to get it on a 16-millimetre camera.''

The magazines for their movie camera were the only source of unexposed colour film left in the cabin. Bean continued his commentary.

"It looks like this is going to have an illuminated atmosphere, probably the whole time it's eclipsed. The Sun is set, but it's so close to the limb that that bright light is being channelled through the atmosphere, and so if you look at it with a naked eye you can't tell if the Sun is set yet. Through the smoked glass, you can see that it's no longer a disk there, but you just see a bright white line the diameter of the Sun.''

Gordon was running out of words to describe the view: "This is really spectacular. Have you got any more adjectives for spectacular? I'd like to use some if you have.'' "No. We'll put somebody to work on that, too,'' replied Weitz. It is often said that when humans went to explore the Moon, what they really discovered was Earth. This was literally coming true for the crew of Apollo 12. Because the Sun had gone behind Earth, their eyes could adapt to the darkness and detail was becoming visible across the night-time hemisphere of Earth, illuminated by sunlight reflected from the Moon.

"This has got to be the most spectacular sight of the whole flight.'' Bean was also running short of adjectives. "Now that the Sun's behind the Earth, we can see clouds on the dark part of the Earth; and, of course, the Earth's still defined by this thin blue-and-red segmented band. It's a little bit thicker down where the Sun just set than it is at the other one, but it is really a fantastic sight. The clouds appear sort of pinkish grey, and they're scattered all the way around the Earth.''

Gordon began to see further detail on Earth's dark face. "Say, Houston. It's very interesting. We can see lightning and the thunderstorms down there on the Earth. You can see it quite clearly, flashing from wherever we are.''

"Yes. They look sort of just like fireflies down there blinking off and on,'' added Bean. They were now less than 50,000 kilometres out and approaching the height of the geostationary communications satellites.

"We're starting to look out for these synchronous satellites now,'' said Bean. "We've been looking ahead.''

"Sure hate to run into one up here,'' added Conrad. "Yes. It could ruin your day,'' agreed Weitz.

As Earth's sunset lightshow continued, the crew fished out their monocular to get a closer look.

''We're better night-adapted now,'' said Conrad, ''and by golly, we can see India, and we can see the Red Sea, and we can see the Indian Ocean quite clearly. It's amazing how we can see, for that matter. We can see Burma and the clouds going around the coastline of Burma, and we can see Africa and the Gulf of Aqaba. We can also distinguish the lights of large towns with our naked eye, just barely, and by using the monocular, we can confirm that that's what we're seeing.'' Conrad was getting into his stride.

''There's a couple of ripdoozer thunderstorms down there that are really, really letting go. There seems to be a weather system out there, and it's got thunderstorms all the way along it. Venus is just below the Earth, and we can see Venus quite clearly. This is really a sight to behold, to see it at night-time like this. And looking at the airglow with the monocular is - Boy, there is another sight now that is not like being in Earth orbit whatsoever. It's a bright red, next to the Earth, and then it's got a green band in it, and then it's got a blue band.''

''Would you say these colour bands encircle the Earth now, Pete?'' asked Weitz. ''Yes,'' replied Conrad. ''But it's not the same all the way around. What I'm seeing is sunrise, really. This is about 40 degrees from the Sun, and there's a bright red band, and then a sort of a light green band that's very thin, and then a blue one which must be all of the atmosphere.''

The crew of Apollo 12 were deeply struck by what they had seen and made a point about it after the flight. ''We all were caught with our pants down,'' said Conrad during the debriefing. ''We should have had good camera settings and film available for that because it was certainly a spectacular sight.''

''I feel very strongly about this,'' added Gordon. ''I think that someone, the crew as much as anyone, really dropped the ball on this. We knew this was going to occur before flight and we mentioned it. It was a very poorly handled phenomenon we all knew about before the flight.''

The Apollo 15 crew witnessed a different type of eclipse during their return flight. It was not the spacecraft that entered Earth's shadow, it was the Moon. This was a lunar eclipse and it was visible across half of the world. However, unlike those on Earth who were watching from within the cone of the shadow, the crew of Endeavour had the benefit of a side-on view of the entire spectacle. While they coasted to Earth, the Moon continued in its orbit such that 2 days into the coast, they were substantially to one side of the Moon-Earth line. When the Moon passed into the shadow, they had a perspective on the event that has never been repeated.

When Earth's shadow crosses the Moon's disk, viewers on Earth can see the arc of our planet projected onto the lunar surface, which is classic proof that the world is round, familiar even to the ancient Greeks. But from Endeavour's position, well off to the side, the shape of the Moon altered the apparent line of the Earth's shadow such that, at the start of the eclipse, the curve of the shadow was more than cancelled out. Two hours later, when the Moon exited the shadow, its shape reinforced the curve of the Earth and produced a very strong crescent effect.

Once the Moon had completely entered the umbra, it was no longer lit directly by the Sun. However, had Scott and Irwin been standing at Hadley Base at this time (and thankfully, they weren't), they could have looked up at the Earth and seen a similar awe-inspiring sight of 40,000 kilometres of sunset and sunrise all around the globe forming a ring of gold in the sky. Unfortunately, their rover's TV camera had long since stopped working after a circuit breaker in its power supply had opened in the heat of the lunar day. During that moment, shared by half a world and the occupants of Endeavour, this golden ring turned the eclipsed Moon a dark, copper-brown colour.

Irwin described what he could see: ''Right now the Moon varies from a very pale orange to a good deep burnt orange on one side and a very gradual change. It certainly is pretty.''

''Very good,'' replied Karl Henize, himself an astronomer as well as an astronaut. ''It sounds like a beautiful view from up there. You've seen a lunar eclipse of the Moon twice as big as anyone else has ever seen such an eclipse.''

''That was very interesting,'' said Irwin, ''It'd be a great place for somebody like you to come up and use your trained eye to interpret all this and understand it.''

''Sounds like it would be fun, someday,'' agreed Henize.

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