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Photos of the our milky way galaxy

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  1. May 2, 2009 #1
    I have seen several photos of the our milky way galaxy, other galaxies and some photos of even 100's of galaxies in the same picture.

    How do they do it? Usually if you see in the sky, all you see is the stars. (naked eyes)
    I believe to be able to see actual of our milky way galaxy we need to be very very far from it; but we are part of it. How can we see it even with the best telescopes?

    I have read there are highly sophisticated telescopes that watches the space for quite a long time to get a picture of 100s of galaxies but would like some detailes explanation on how is it done?
     
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  3. May 2, 2009 #2

    Integral

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    Re: Photographs

    You have never seen a picture of any more then a portion of a arm of our galaxy. That is all we can see, any images of OUR galaxy that you have seen must be an artists rendition.

    Other galaxies are easy, just point a large telescope at the sky and let it soak up light for a while. How long a while, I am not sure.
     
  4. May 2, 2009 #3

    mgb_phys

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    Re: Photographs

    You can't see the whole of our galaxy because we are in it .
    You can see part of the galaxy (from us to the centre) - on a dark site in the south it looks like a wide band of stars, like a cloud across the sky.
    Photographs can show up many 1000s more stars and so make it look more solid.
     
  5. May 2, 2009 #4

    Nabeshin

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    Re: Photographs

    Exactly like Integral said, to get images of 100's of galaxies you just point your telescope at one part of the sky for a long long time.

    One of my professors in astronomy was involved in the Hubble Deep Field observations, which basically consisted of taking the HST and pointing it at one patch in the sky for about 150 orbits around the earth. The result is this:
    http://upload.wikimedia.org/wikipedia/commons/5/5f/HubbleDeepField.800px.jpg

    It doesn't really take a sophisticated telescope, just a lot of patience :)
     
  6. May 2, 2009 #5
    Re: Photographs

    Thanks for all your answers. This picture is really cool. Could you please explain what does it mean by "long long time" I am sorry I really don't know much about telescopes. I believe when you look at a telescope you see stuff. What difference it makes if you see it for longer time?

    Also what does it mean by "150 orbits around the earth"?
     
  7. May 2, 2009 #6

    mgb_phys

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    Re: Photographs

    The Hubble deep field (the above image) is about 30-40 hour exposure in each of 4 colours.
    Scientific cameras are black+white with a filter to select the colour.

    The telescope (HST) is in space and it took about 10days to make all the exposures, during which the telescope orbited the earth 150 times.
    Ground based telescopes are larger and in some colours can see fainter object (although with less sharpness) but they can't observe the same point for 40hours at a time - dawn gets in the way!
     
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