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Stars from the Moon


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I watched the Sky At Night last might and the brief interview with Neil Armstrong in which he said that you can't see any stars from the moon, only the Earth and the Sun. Can anyone explain why this is

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This is the example i'd give. If you go out into your street on the next clear night and luck up while standing next to a lamp post you'll see nothing because to lamp is washing out the stars. Next go

Because the Sun is so bright, it's just like the same reason we can't see the stars in the daytime on Earth. The brightness of the Sun overpowers the faint glimmers of the stars.

I suppose though given a nice EQ mount and long exposures then you would see the stars come alive.

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Exactly. When they were on the moon it was day-time (which lasts for about 2 weeks on the moon). The 'sky' remains black as there's no atmosphere but there's no chance of seeing stars. I assume if they were on the 'night-time' half of the moon then they would be visible. It's worth looking at the videos of the stars from the ISS on Vimeo. Stunning!

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Are you sure? I thought it was just in photographs that you couldn't see stars from the moon because of the short exposure. I would have thought the dynamic range of the eye was plenty good enough to see stars..?

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Not much of a chance in seeing stars at any time on the near side of the moon. The sun will be too bright during the day (like on earth) and the earth will reflect massive amounts of light at luna night (like a full moon does to us mere mortals). It would be a different story if you were to look out from the far side of the moon when we view it as a full moon. Then you would see the whole universe in absolute dark, the perfect place for an observatory!

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Are you sure? I thought it was just in photographs that you couldn't see stars from the moon because of the short exposure. I would have thought the dynamic range of the eye was plenty good enough to see stars..?

Sun is aparent magnitude -27, the eye has a huge dynamic range, but thats about 50,000 times brighter than a mag 0 star. Its not that much

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At the real risk of being proven wrong/dumb, I'm going to keep my neck stuck out and say that you would be able to see stars! I understand that the sun is bright, but you could always look in the other direction for a while until your eyes adapt, no?

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You would be able to see stars on the moon if you screened all glare coming from the sun, from the lunar surface, and from the helmet visor. Armstrong evidently didn't do this so he didn't see stars.

Two things stop us seeing stars in daytime: skyglow (scattered light from the sun, making the sky blue) and glare. Cutting daytime glare does nothing to eliminate terretrial skyglow, but on the moon this would be possible. Just blocking the sun itself would probably not be enough because of the brilliance of the lunar terrain. Also you'll note that the astronaut's helmets were reflective, so they must have transmitted only a fraction of the available light. Armstrong's situtation was analogous to being in a snowfield with sunglasses - not the best way to see stars. And he had a lot of other stuff to get on with as well.

Though just to clarify the snowfield analogy - lunar soil is actually as black as charcoal, but in strong sunlight it would be dazzling. the lunar landings were deliberately timed when the sun was low in the lunar sky, to reduce potentially harmful exposure to solar radiation, but the sun would still be just as bright to the eye when near the lunar horizon as when overhead, since there is no atmospheric extinction. So Armstrong's eyes were adapted to daylight levels (even alloowing for his reflective visor) - he had no chance of seeing stars.

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Edit: apologies for typos in previous post. Also first statement should be expanded:

You would be able to see stars on the moon if you screened all glare coming from the sun, from the lunar surface, and from the helmet visor. And if you waited up to half an hour for your eye to dark adapt once you had screened out the light sources, and made sure you wore a visor with sufficiently high light transmission. Armstrong evidently didn't do this so he didn't see stars.

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This is the example i'd give. If you go out into your street on the next clear night and luck up while standing next to a lamp post you'll see nothing because to lamp is washing out the stars. Next go into your garden or shield the lamp with your hand and you will begin to/ or see stars. Same principle with the Sun.

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Something tells me Neil Armstrong would know a star when he saw one... So i think aside all the arguments here we can safely say he didn't see any :p

Considering he was looking through a tinted suit mask and have the glare of the earth/sun to contend with, this doesn't surprise me.

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In the press conference after apollo 11 all 3 astronauts said that they cound not see any stars without using optics. Even Michael Collings that only orbited the moon ( and passed a lot of time in the dark side of the moon) positively said don't see any star.

At: 48:20

the question is, There are many interviews with astronauts who speak the contrary, it is possible to see stars in space, even during daylight.

Astronauta Edward T. Lu

"Mars ... is bright enough that even when we are on the lit side of the Earth, and with all the lights on inside,

it is clearly visible against the black background of space. "

http://spaceflight.nasa.gov/station/crew/exp7/luletters/lu_letter11.html

Mike Melville, first man in a privately funded suborbital trip.

"Seeing the bright blue sky turning pitch-black and seeing stars appear while it is day time is absolutely mind-blowing."

http://www.iol.co.za/news/south-africa/astronaut-visits-sa-after-spaceshipone-trip-1.237528#.UJQCJGfbTpc

Astronaut Dra Kalpana Chaw

"The coolest thing for me is the experience of floating, not

feeling my weight, and hanging by a window, just after sunset, and watch the stars in the big black dome of

the sky, as the Earth moves underneath. I somehow try to find 10 - 15 minutes every day to do that.

I think most mornings I try to continue to postpone my meals so I can do that. It's kind of fun because I have

to watch where the food is going because my eyes are really glued to the outside. It is just absolutely amazing,

magical, wonderful feeling to do that."

At:1:04

Omitting the sight of the stars and the closure of the matter is much easier than one possible unrealistic explanation of how it would be spend the entire trip surrounded by them without giving the slightest importance to this fact....

sorry for the mistakes in English, because I'm not fluent in that language.

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Just my two cents; If you were at one of the 'edges' of the visible moon, say in Mare Crisium a few hours after sunset, and having only a 'crescent Earth' to contend with, and given a clear visor, you should be able to see lots and lots of stars. None of the Moon landings were in such a position. I'm a little surprised Collins didn't see any stars on the nightside, though.

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I think the solution to the question is with the function of the human eye. Because the eye is exposed to all light (not just what's reflected off objects focused on) through periferal vision, any bright light in it would constrict the pupil down to a point where any much fainter light (stars) would not be visible. Even if the Sun's light were shaded on the Moon and the Earth (and other bright objects in the sky) not visible at the time, the Sun's light reflecting off the surrounding lunar ground would be enough to cause the pupil to constrict from the scattering of reflected light in the eyeball's inner fluid. From a spacecraft? I believe all their viewing ports use tinted glass as their helmet visors do and that amount of tint would stop stars from being seen with no other light source (a darkened cabin enclosure) present.

I'm just guessing this may be the answer :Envy:

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The moon's orbit is locked in so Earth would be in the same position overhead at all times. If you think how many fewer stars we can see when the full moon is in the sky, it's not surprising that the sun, the earth and the reflected light of both off the surface below the astronauts' feet would have combined to wash out the much fainter starlight.

Anyway if Neil Armstrong says he didn't see any stars, I know of no reason not to believe him! :)

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Would the earth be in the position everyday? I don't think so. Rememmber the famous 'earthrise'photo from the appollo missions. It can't rise if it was always in the same position. Also the moon doesn't orbit on the same plane, hence why we get eclipses somettime.

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Two things to consider, as I wrote above, the three astronauts of Apollo11 do not see stars, even when orbiting the moon (as was only the case of Michael Collings).

This interview shows that even in the path between the earth and the moon Neil Armstrong said the space is deep black and starless.

As exemplified also, This contradicts various experiences of current astronauts who claim that the view of the stars is perfectly possible, even in the light side of the Earth and the cabin lights on.

Another thing, the fact that we can not see stars clearly during the full moon here on Earth, is due to the fact we can not even see them during our day, because of the strong scattering of light from the moon by our atmosphere, factor nonexistent on the moon. Even during the day on the moon, just the fact of being in the shadow - for adjustment of the pupil - of any object, the lunar module for example, would be enough to see the sky full of stars, because the Moon's reflection (albedo) is only 8%, negligible compared to 35% of the Earth.

Understand that I am not trying to prove any conspiracy theory, but these facts are very intriguing to at least show an attempt to manipulate the informations.

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Matt - the way to think about it is, the moon always points the same way at us (hence the man in the moon and the far side that we never see). So if you stand on the side of the moon facing earth, the earth will always be in the same position in the sky. If you stand on the other side, you'll never see the earth at all.

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Not sure about why they could not see stars on the way to the moon, but I think once on the surface the answer is simply contrast: don't forget they were wearing thick visors with poor contrast, and the environment was very dusty. They had major problems with all the dust they tracked back into the lunar module.

I suppose the reason they didn't see any stars on the way to the moon is also simple: it was probably cloudy! :-)

Edited by Ags
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You must remember that Neil Armstrong would have been looking through a very dark visor to counteract the sunlight on the moon surface, so this too would have stopped him seeing stars. I feel that if you kept the Earth and sun from your field of view (as per the previous wonderful example of a bog roll!!) you should be able to see the stars. If there is nothing bright in your line of sight your dark adaption should be good, and with no atmosphere to scatter the light - you are in fact to all intents and purposes in a vacuum so stars would be visible.

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THe atmosphere does not form an airey disc - that is formed by the diffraction of the optical system bringing the light to focus. So everything we see with our eyes has an airey disc, because our pupil has an edge that causes diffraction. But regardless of that the image is formed by photons hitting the retina and causing a chemical reaction, it's got nothing to do with the specific diffraction pattern formed by the optics.

Edited by Ags
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Armstrong's visor was set to filter out direct sunlight that ahd no attenuation from the non-existant atmosphere.

The stars are simply too far away and too dim to get through that level of attenuation on their visors.

You cannot look at the sun through the earths atmosphere, it is a LOT more intense above the atmosphere.

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