Why are there no stars visible in cislunar space?

  • It’s very puzzling that the moon landing had no stars in the background, the ISS clips have no stars in the background. I listened to multiple astronaut interviews speak on what it looks like up in space and about half of them speak of the “darkest black space”. I’m sure there is a very good explanation for this.



    Is star light only visible through the medium of earth atmosphere? But once in the vacuum of space where there is no medium they disappear? What’s the explanation?



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    Minute 47-49 stars, press conference all three Apollo 11 astronauts



    BBC interview with Neil Armstrong only


    I’m sorry, I did search my question prior to posting it but this did not come up. Thank you for that.

    *no need* for "I'm sorry!" That's in a different Stack Exchange site, so it is not a duplicate. It's just nice to add links to related questions in different sites so future readers can have more to read. I'll add a comment there as well.

    That makes sense, it wasn’t obvious to me when I clicked the link that I was in a different stack, until you pointed it out that it was a different stack. Once again thank you for the link.

    It might be interesting that the visibility of stars from the Lunar surface, by human eye and news camera, was a minor plot point in Arthur C Clarke's novel _A Fall of Moondust_, published in 1961.

    NASA does have some Black Marble images of the dark side of the Earth, but they appear to be assembled from narrow-angle satellite images so they don't have any stars either.

    Ever tried to take a picture of someone with the stars as a backdrop?

    Not in space I haven’t. But I’d image with the lack of pollution and light pollution whilst in the moon’s shadow the stars would have been brilliantly lit.

    And as seen in @Luaan's answer, he testified that they *were* visible while in the moon's shadow.

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  • Luaan

    Luaan Correct answer

    3 years ago

    Anders's answer is entirely fine, but I'd like to add some extra information. As evidenced by the transcripts, reflected Earth light is quite strong even at this distance:




    The earthshine coming through the window is so bright you can read a book by it.




    That is, even with the lights turned off, it would probably be tricky to see the stars unless you turned in a way that didn't allow the earthshine through the windows.



    However, as the capsule comes into the shadow cast by the Moon (a pure accident - they didn't plan for the approach to go this way), there comes:




    Houston, it's been a real change for us. Now we are able to see stars again and recognize constellations for the first time on the trip. It's - the sky is full of stars. Just like the nightside of Earth. But all the way here, we have only been able to see stars occasionally and perhaps through the monocular, but not recognize any star patterns.




    So for a few minutes, they did see "the sky full of stars". Other than that, they've seen a few stars once in a while, but only singular, bright stars (perhaps also when looking in a way that minimized the brightness from the Earth and Sun):




    Houston, it's been a real change for us. Now we are able to see stars again and recognize constellations for the first time on the trip. It's - the sky is full of stars. Just like the nightside of Earth. But all the way here, we have only been able to see stars occasionally and perhaps through the monocular, but not recognize any star patterns.




    The core of Anders's answer is still true, though. Exposure is the main problem here - both cameras and human eyes have a certain dynamic range, and even the brightest stars are entirely too dim in comparison with both the Sun, the Earth (in distance comparable to the Moon's distance from the Earth) and the Lunar surface (if you're in sunshine, as most of the mission was). A modern camera might be able to take a HDR picture that would allow the stars to be visible at the same time as the Earth or the Sun, and it'd be quite easy to do if you could occlude the main light sources (the same way we do it when photographing the Sun's corona etc.). But technically, that would be a "doctored" image - taken at two different exposures and combined in a way that uses different exposures for different parts of the image.


    Could you please refer me to transcript you are quoting from and the year of publication from the corresponding Apollo mission. Thank you.

    @Autodidact Comes straight from NASA for Apollo 11 - https://www.hq.nasa.gov/alsj/a11/a11transcript_tec.html. It's right at the end of the third day in mission time, but you can easily find the quotes with a text search anyway.

    Neil Armstrong claimed to have also been in the moon’s shadow and seen a corona from the sun which poses a problem in itself because the moon should completely cover the sun the closer you approach but certainly if the Apollo 11 mission whilst in the moon’s shadow could see the stars why didn’t Neil Armstrong? *“However, as the capsule comes into the shadow cast by the Moon“* @Luaan.

    @Autodidact Those quotes are from Neil Armstrong (in the transcript, he's CDR). I don't think it gets any clearer than that :) And yes, he's also talking about the corona there, describing it's size as "two lunar radii". I don't see why you'd expect the Moon to completely cover the Sun the closer you approach - you're not heading for the center of the Moon, you're inserting yourself into a lunar orbit. Even then, the Moon only obstructs the Sun if it's in the same direction as the Moon from your point.

    I just realized that now. Which makes even less sense given his interview where he said he never saw ANY stars. https://m.youtube.com/watch?v=PtdcdxvNI1o

    as for your corona question *”A corona comes during a solar eclipse. A solar eclipse starts in the day. To form, Earth moves behind the Moon, leaving sunlight on the Moon. Use sunglasses to protect your eyes. When you look at the Moon, the corona sticks out on the edge of the Moon.”* So I’m trying to visualize how if the moon is offset as most of the times there is no solar eclipse on earth the astronauts would still have seen the corona, based also on your comment. Maybe you can enlighten me. Thank you in advance.

    @Autodidact, two thoughts based on your comments: 1) He was speaking specifically about the view while on the moon, and specifically stated that it was different from cislunar space. 2) They were in transit between Earth and Moon, so were in a position to see the corona at the edge of the lunar disk. I.e. their position *was* eclipsed, even though the Earth was not.

    He said the only things visible, that’s in the positive tense and then proceeds to enumerate. But I agree there is a difference between the two statements. Likewise if I hold a round dinner plate at distance tocover the sun and expose the corona and then proceed toward the plate do you think the corona will continue to be visible or the closer I get the greater my view will become obstructed by the dinner plate until I’m right in front and it completely covers my line of sight obstructing everything from view. Same with being in the shadow of the moon closer to the moon than on earth.

    @Autodidact You responded to something I later edited out of my comment. However, the flaw in your reasoning (as pointed out above) is that they were not traveling directly toward the center of the moon, but to an orbit around it. They passed through the shadow, but were navigating toward its edge. And in any case, he did not state that the corona was visible during the entire transit of the shadow, only that it was visible specifically at the edge of the shadow.

    @Autodidact And to reiterate: the interviewer *specifically* asked about the view *from the surface of the moon* (not in cislunar space) and Armstrong *specifically* answered that question followed by a *specific* statement that the view from the lunar surface differed from that in cislunar space. This is all in the first question/response of the interview.

    @GalacticCowboy *”The sky is a deep black as viewed from the moon, as it is when viewed from cislunar space...”* N. Armstrong in the link I provided from the BBC. Are you watching a different documentary or interview? Also the reporter said he had very little time to look up and yet he was on the moon for 22 hours. But anyway. I wasn’t there, it doesn’t explain the lack of stars being visible and I’m sure there is a very good explanation. Michael Collins in a different interview despite circling around the moon even on the dark side and moon shadow said *“I don’t remember seeing any (stars)”*.

    @Autodidact You are correct, I misheard his statement. However, you're still getting hung up on something - you've been given multiple very good reasons throughout this answer as to why stars would not always be easily visible from space, yet you reject those reasons without explaining why you have rejected them. For example, in all of the photos you posted, the subject is in very bright light and the background is in either sunlight, earthlight, or both.

    @GalacticCowboy my question also includes referencing eye witness testimonials of astronauts. I could try to post those too like I have of the BBC clip not just photos. But I didn’t disagree with the answers. I said that makes sense. I started asking questions when Luaan said that they did see stars on occasion and then I got confused because I was fine with no visible stars and the explanations given.

    @Autodidact - he was on the moon for 22 hours but outside of the LEM for just 138 (rather busy) minutes. The two main windows looked out over the lunar surface with only a rather small overhead window to help with docking with the CM: seeing stars through that while standing on the floor of the LEM would have been hard, especially with the glare of the lunar surface coming through the windows (Armstrong & Aldrin reported that even with the window blinds drawn and cabin lighting off it was too bright to sleep effectively)

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Content dated before 7/24/2021 11:53 AM