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Author Topic: Why does footage shot in space not show stars?  (Read 2693 times)

Thys Smit

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Why does footage shot in space not show stars?
« on: 28/10/2009 17:30:06 »
Thys Smit  asked the Naked Scientists:
   
Why can we see the light emitted from stars from earth even through our polluted atmosphere, but I have never seen any stars on any photos taken by NASA or anyone else for that matter while in orbit or outside the atmosphere of the earth. Also one does not see any stars in any video footage shot in space. Why is that?
 
Thys Smit
Johannesburg
South Africa

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Offline rosy

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Why does footage shot in space not show stars?
« Reply #1 on: 28/10/2009 18:13:54 »
In order to take photos of stars you need pretty long exposure times (or very, very sensitive film/cameras), even in space. If you're filming (say) someone moving about outside a space station, they're going to have to be pretty strongly illuminated to get any footage at all of the person /thing being filmed (since the exposure time is limited by the need to shoot 30 frames per second, or whatever is the required speed), either by the sun or by a damn great light akin to a camera flash.
 

Offline LeeE

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Why does footage shot in space not show stars?
« Reply #2 on: 28/10/2009 19:42:49 »
Why can we see the light emitted from stars from earth even through our polluted atmosphere, but I have never seen any stars on any photos taken by NASA or anyone else for that matter while in orbit or outside the atmosphere of the earth. Also one does not see any stars in any video footage shot in space. Why is that?

It is for the same reason that we can't see the stars during the daytime.

The light from our sun, coming from only 8 light minutes away, is much brighter than the light coming from the stars, which are several, to many, light years away.

The problem arises because the dynamic range of our eyes and cameras, or in other words, the range of brightness that they can cope with, is limited.  Both our eyes and cameras can shift this range up and down by quite a lot though, so that we don't get dazzled and blinded when it's bright and sunny, but we can still see to some degree at night when it's dark and there's only moon light or artificial light to see by.

When we look at photos or videos of people in space they're in bright sunlight so our eyes or cameras have to shift their range to avoid being taking in more light than they can cope with.  This means though, that the relatively dim light from the stars now falls outside the dynamic range and they're just too dim to see.

If you think about how we sometimes need to wear sunglasses on bright days to feel comfortable, and how a bright light at night doesn't seem nearly as bright during the daytime, what you're seeing there is the effect of that limited dynamic range.
 

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Why does footage shot in space not show stars?
« Reply #2 on: 28/10/2009 19:42:49 »

 

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