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Thread: question about the distance stars are with the naked eye and with telescopes

  1. #1 question about the distance stars are with the naked eye and with telescopes 
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    When I look at Betelgeuse with my naked eye, I see it as it was 450 years ago. When I look at it with my 10" telescope with a powerful eyepiece, I'm seeing it further in the future. If it was possible could you look through a very powerful scope and see it as it is today? I realize the mirror would have to be very large. I have often wondered this. Thanks. Filix.


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    Bullshit Intolerant PhDemon's Avatar
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    No, when you use your telescope the image is bigger but the light has still taken the same amount of time to reach you!


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    Quote Originally Posted by filix View Post
    When I look at Betelgeuse with my naked eye, I see it as it was 450 years ago. When I look at it with my 10" telescope with a powerful eyepiece, I'm seeing it further in the future.

    Huh? The more distant the object viewed, the older the light you are seeing.


    If it was possible could you look through a very powerful scope and see it as it is today? I realize the mirror would have to be very large. I have often wondered this. Thanks. Filix.
    Light travels at a finite speed. The more distant the object, the longer it has taken for that light to reach you. When you look into a mirror, you are seeing yourself as you were a nanosecond ago. When you look at our sun, you are seeing it as it was about eight minutes ago. See the pattern? So, no, you can't even see yourself as you are today. You are always seeing things as they were, not as they are.
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    Quote Originally Posted by filix View Post
    When I look at Betelgeuse with my naked eye, I see it as it was 450 years ago. When I look at it with my 10" telescope with a powerful eyepiece, I'm seeing it further in the future. If it was possible could you look through a very powerful scope and see it as it is today? I realize the mirror would have to be very large. I have often wondered this. Thanks. Filix.
    You are seeing 450 year old photons being refracted by the telescopes optics to magnify betegeuse.
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    Quote Originally Posted by filix View Post
    When I look at Betelgeuse with my naked eye, I see it as it was 450 years ago. When I look at it with my 10" telescope with a powerful eyepiece, I'm seeing it further in the future. If it was possible could you look through a very powerful scope and see it as it is today? I realize the mirror would have to be very large. I have often wondered this. Thanks. Filix.
    There are two basic types of telescopes, the refractor, which uses just lenses and the reflector, which uses a combination of mirrors and lenses.
    They both basically work by gathering light from a larger area than your pupil and bending the light paths as to increase the size of the image in your field of view. The extra light gathered also allows you to see things that would have been too dim to see by naked eye alone.
    Simple refractor diagram:
    http://www.astronomy.ohio-state.edu/.../refractor.gif

    Simple reflector diagram:
    http://hosting.astro.cornell.edu/aca..._newtonian.gif

    In both cases, the light reaching the telescope is the same light as would have reached your naked-eye and you are still seeing 450 yr old light through the telescope. If anything, the light you see in through the telescope is just the tiniest bit older than the light you would see by naked eye. The light has to pass through the lens material, in which light travels slower than it does through air, and in the case of the reflector, it actually travels a slightly longer distance before reaching your eye. This delay is, for all practical purposes, insignificant ( who cares about an few additional nanoseconds over a 450 yr journey?)
    "Men are apt to mistake the strength of their feelings for the strength of their argument.
    The heated mind resents the chill touch & relentless scrutiny of logic"-W.E. Gladstone


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    Thanks a lot. I get it. Its profound! The only way to see Betelgeuse as it is , is to go there. Which is currently impossible. If you could get there, you couldn't get too close. So it would still be in the past. Once more, it might not be there at all. Filix.
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