Astronauts stand at the meeting point of heroism and celebrity. As do other explorers, they have to their credit genuine, real-world accomplishments that take guts as well as know-how and talent. But although they go into space as representatives of a country, and although it takes a quasi-military organization such as NASA to get them there, they are regarded as individuals.

One of the astronaut subjects of David Sington’s “In the Shadow of the Moon” tells of how after he had gone to the moon, wherever he went, in every country, people would say not that America did it, but that the whole human race accomplished something. That’s the hallmark of the celebrity. He makes his audience a participant in his fame.

But Mr. Sington’s documentary is not a celebrity vehicle. It celebrates real heroism and a consciousness of the heroic, mainly of the astronauts in relation to one another. Neil Armstrong does not appear — his refusal to give interviews adds to the air of heroic mystery about him — but he is clearly regarded as a hero by the others.

Brigadier General Charlie Duke speaks of him almost with awe as “Dr. Cool” and remembers an occasion when, after almost being killed in a sudden bailout from the prototype Lunar Lander, Mr. Armstrong immediately went back to his cubicle and shuffled papers. Just another day at the office. “That’s what you had to do,” General Duke says. “The mission goes on.”

Like all true heroes, these men admire the heroism of others while being modest about their own heroism. Captain Alan Bean says his heart rate shot up to 140 beats per minute upon launch, while John Young’s stayed at a steady 70. “I was too old for it to go any faster,” Mr. Young says.

It’s Captain Bean who, along with General Duke and Major General Michael Collins, has the most to say about his experience, and he says some of the most interesting things. Captain Bean notes, for instance, that after Tom Wolfe’s “The Right Stuff” came out, he was amazed. “I’m the same guy I always was, but now I’ve got the right stuff!”

Later, it’s Captain Bean, too, who says of Mr. Armstrong’s pushing the limit on the Lunar Lander’s fuel in order to find a place to land on that first mission: “No astronaut is going to say, ‘I got low on fuel and decided to turn around.’ No astronaut is going to do that. It wouldn’t be the right stuff.”

To some it will seem a telling detail that, at least to this extent, the astronauts learned how to be astronauts from Mr. Wolfe — just as (so we are told in “The Sopranos,” anyway) mafiosi have learned how to be mafiosi from “The Godfather.” But heroism is always a collaboration among the heroes and those who tell their stories. How would we know what heroes were without the tradition of heroic narrative, going back to Homer? These astronauts also still see themselves as part of a larger heroic narrative that was set in motion in May 1961, when President Kennedy said, “I believe that this nation should commit itself to achieving the goal, before this decade is out, of landing a man on the moon and returning him safely to the Earth.”

Although Kennedy said in the same speech that “we go into space because, whatever mankind must undertake, free men must fully share,” the speech itself added another reason by its implicit pledge of nation’s honor to get to the moon — and to get there first. We learn from “In the Shadow of the Moon” that the launch of Apollo 8, in December 1968, hadn’t originally been intended as a moon shot, but rumors reported by the CIA that the Russians were about to try one made NASA change it to a moon mission, though not yet a landing.

Thus General Duke speaks of the successful landing and the astronauts’ satisfaction with it as a “great sense of accomplishment for President Kennedy and the nation. We did what we said we were going to do.”

Colonel Dave Scott, who was the commander of Apollo 15 in the summer of 1971, makes the very interesting point that in all the science fiction versions of travel to the moon, “I don’t think any of them imagined the whole world watching on TV.” That single detail had the potential to turn the astronauts from heroes into celebrities. We should be grateful that, by and large, they have resisted this temptation.

Instead, as one of them so memorably puts it in this film, they seem to have felt, upon their return from the moon, that people were looking at them and saying: “‘This guy walked on the moon.’ Now I have to uphold that for the rest of my life.”

This terrific movie shows us the men, now in their 70s, who have upheld that legacy.