I’m not one of those people who subscribe to the theory that the moon landings were a hoax, but why is it that you can’t see any stars in the astronauts’ photos from the lunar surface?
When you visit the desert, for example, the stellar display is spectacular. One would imagine, then, that the moon, by proxy, being bereft of any atmosphere, would showcase stars galore.
Instead, the lunar sky always appears to be black. What gives?
I’m sure some samrtass will look up some “facts” or something to prove me wrong, but…
It was daytime. The big old bright sun drowned out the starlight.
It wasn’t always daytime there. Yet you NEVER see any stars.
This topic has popped up before on the SDMB, and elsewhere. A good site is http://www.badastronomy.com . The explanation is that the light reflected from the lunar surface is far, far brighter than the stars, so if you set your camera aperture low enough to keep your nearby lunar surface from “washing out” the image, the stars are far too dim to make an impression. nd if you open the aperture up (but still have the surface in view), it’ll still wash out the image. The only solution is to look up, away from the surface, the LEM, and your fellow astronauts and open up wide, and I don’t think they ever did that.
Come to think of it, I’ve never seen lunar pictures taken at “night”. Bear in mind that a lunar “day” is half a month long, and lunar missions only spent a couple of Earth days on the surface – during the Lunar “day”, of course.
Here is a thread which answers this and other questions.
The moon has an extremely high albedo, meaning it reflects a LOT of light (more than most things on Earth, I believe). The stars, by comparison, are much dimmer than the bright lunar surface.
The equipment used at the time simply wasn’t able to span the contrast presented by the two images. If the picture was exposed for the lunar surface, the stars would be too dim to see (as happened); if the image was exposed for the stars, the moon would be an undifferentiated blob of light. Since the moon’s surface was what we all wanted to see, that was what was exposed properly, rendering the stars invisible.
Anyway, just a WAG from what I know of photography.
On a related note, what exactly was used to take the moving images we see? Video was nascent at the time, so was it 8mm film or the like? How about the still pictures? Are they frames from the video/film, or are they from a still camera (i.e., 35mm)?
STARK sez
Your information about contrast was correct but the moon does not, in fact, have a high albedo. It is quite low – about the same as basalt. (It is, after all just dusty old rock.)
And the Apollo missions were, of course, deliberately scheduled to occur during the lunar day – actually more like late afternoon in order to have useful shadows. Astronauts out in the lunar night would get very cold. Worse than in space, actually because heat could be conducted away where they were in contact with the cold lunar surface. But lighting was their primary consideration.
Films were photographs, not video, and stills were taken separately. The astronauts used Hasselblad (sp?) cameras for stills. I don’t know the film size but IIRC it was larger than 35mm – isn’t there a 3"x4" format? They didn’t skimp on photographic equipment since photographs were one of the primary results of these enormously expensive missions.
In essence, it is always day on the Moon. The same face is always facing Earth. You can’t walk outside at high noon and expect to see stars, other than the Sun. The same hold true on the Moon.
A day on the Moon lasts about a month, but the sun rises and sets just like here.
The Apollo landings were done on the side of the Moon nearest the Earth, and were timed so that it would be in sunlight while they were there.
pluto: thanks for the correction. I just checked out a chart of planetary albedos and you’re right; the moon’s is pretty low.
But you say
Eh? I’m not sure I understand that. Films were photographs? Do you mean that the moving pictures were shot on moving film (rather than video)?
Hasselblad is indeed a maker of medium format cameras, though I’m not sure if 3x4" format is what they use, as I’m a 35mm guy.
adam yax, you say
True, but in essence, it’s always day on Earth, too – somewhere. In other words, the earth is always in sunlight on half its face, just as is the moon.
There is indeed ‘night’ on the face of the moon we see; it’s called a new moon.
Ya know, the earth-centre model of the universe is at least several decades out of date. “night” and “day” for any point on and body in the solar system are defined by that point’s position relative to the sun.
Of course it isn’t always day on the moon, but it was always day on the moon when astronauts were taking pictures.
I also don’t subscribe to the moon landing hoax, but everytime I see the footage I can clearly see through the astronauts, like they’re transparent. Maybe it somehting to do with the equipment but it always looked odd.
Also, why don’t we call russian space explorers astronauts? I’ve always seen the word cosmonaut as a political distinction rather than a semantical one.
FWIW, remember that this the live shots were 1960’s vintage video signals shot across one-quarter of a million miles. No wonder they were noisy. The video cameras had to be smaller than the ones used in the network studios; I wonder if the video tubes just saturated easily, leaving a ghost image of the background.
Regarding the OP: Besides the problems with contrast, they were focusing on stuff at their base camp, so the stars were probably out of focus.
astronauts-exploring the stars (astra)
cosmonauts-exploring the cosmos
mathenauts-exploring abstract math (thank you Norman Kagan)
Yes, it was a political distinction. They did the same thing.
It’s not a political distinction - that’s what the Russians call them. We just use the Russian term when referring to Russian space dudes.
‘Space dudes’ certainly describes the amazing majesty of the work of these men and women.
Just a few points:
The Moon (in general) always has one fact pointed toward the Earth. However, day and night depend on the Sun, not the Earth. If you stand on any spot on the Moon (barring the poles) you’ll have about 14 days of daytime and 14 days of nighttime. The Apollo missions always landed at local dawn to avoid the tremendous heat of lunar midday. It also helps to have shadows from a low Sun, otherwise details are very difficult to see. You can see that for yourself by looking at the Moon through a small 'scope at first quarter versus full. At full moon, details are gone, while at first quarter the shadows give everything some relief.
You don’t see stars in the Apollo shots (or almost any space scenes) because the object being photographed is bright: an astronaut, the lunar landscape, the Shuttle, all are lit by full sunlight. Stars are very faint relative to such bright sources, so you don’t see them in the short exposures. You could see stars in lunar photographs during the day, if you took care to point your camera up, away from the brightly lit ground. I answered this question for Astronomy magazine once: Read my answer here.
Finally, the astronauts look transparent in some of those old videos because of something called persistance''. The old tubes in the cameras would saturate, meaning stuff that didn't move was burned into’’ the camera. So you could see the background even while the astronaut was standing there. You aren’t really seeing through the astronaut, you are just seeing him plus the background. Some people believe this is evidence for a NASA hoax, but that’s silly. You can see the same effect in old TV shows.
I am planning a web page with all these comments on it. I’ll try to remember to post a note here when it goes live.