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Thread: Earth-Based Versus Space-Based Telescopes

  1. #1 Earth-Based Versus Space-Based Telescopes 
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    Hi Friends:

    I'm curious about the advantages of space-based telescopes. Telescopes placed in space are not subject to atmospheric distortions, of course. In what other ways are such telescopes superior to earth-based telescopes? Can't earth-based telescopes offer greater magnification because their large lenses need not fit into the cargo holds of rockets?

    Thanks,

    Jagella


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  3. #2  
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    Without question, best place to mind of Prince for telescope is far side of Moon. Seismically inactive, atmosphere absent, shielded from terrestrial interference of all types(this last of particular benefit to radiotelescopes, and with abundant materials indigenous for construction purposes. With very long baseline interferometry telescope with diameter of Moon itself could be constructed. This prospect is so logical eventually it is virtually inevitable, and sooner is better than later.

    ESA - Space Science - Observations: Very Long Baseline Interferometry (VLBI)


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  4. #3  
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    Yeah, but you are talking many decades in the future (with no funding).

    And there are problems with a moon location. Dust is the major one. Dust is levitated by the electric charges around the terminator and is redeposited. Withouth a method to remove it, any far side telescope will lose effectiveness with time, if it ever gets built.
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  5. #4  
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    Quote Originally Posted by Jagella View Post
    Hi Friends:

    I'm curious about the advantages of space-based telescopes. Telescopes placed in space are not subject to atmospheric distortions, of course.
    "Distortions" is probably too simple: ground based telescopes are blocked by the atmosphere and particulates from smog, clouds, and just the gasses which block, absorb and scatter a good part of the sky's EM spectrum. That we can only view half the sky from any one point is another problem.
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  6. #5  
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    Quote Originally Posted by MeteorWayne View Post
    Yeah, but you are talking many decades in the future (with no funding).

    And there are problems with a moon location. Dust is the major one. Dust is levitated by the electric charges around the terminator and is redeposited. Withouth a method to remove it, any far side telescope will lose effectiveness with time, if it ever gets built.
    Would seem a simple matter to build suitable enclosures for optical instruments as here on planet Earth, where is more dust than Moon by virtue of atmospheric disturbances. Moon has longer night, so dust should settle relatively quickly- and would this be factor for radiotelescopes at all? OP did not stipulate time involved in construction, only pros and cons of space vs Earth location. Lunar night is very cold, advantageous for infrared astronomy, where absence of water vapor is also beneficial, and again, interferometry is possible.

    Infrared astronomy - Wikipedia, the free encyclopedia
    Esteemed moderator is no doubt aware of, but has not mentioned "light pollution" near urban areas which also affect viewing adversely.

    Space wins again, good thread.
    The bravest are surely those who have the clearest vision of what is before them, glory and danger alike, and yet notwithstanding go out to meet it.- Thucydides
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  7. #6  
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    Quote Originally Posted by Lynx_Fox View Post
    "Distortions"is probably too simple: ground based telescopes are blocked by theatmosphere and particulates from smog, clouds, and just the gasseswhich block, absorb and scatter a good part of the sky's EM spectrum.That we can only view half the sky from any one point is anotherproblem.

    I'm wondering how much of a problemsmog, clouds, and gases in the atmosphere are for telescopes in partsof the world in which the skies are relatively clear. Is there anyway to correct for blockages in the atmosphere?


    And what of the advantages ofground-based telescopes? They can be built with larger lenses withgreater magnification. Isn't that true? And they don't need to belaunched into space, of course, which isn't cheap, I'm sure.


    Thanks for pointing out thatground-based telescopes can only view half of the sky. Sometimes themost obvious things escape me.

    Jagella
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  8. #7  
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    Even space based telescopes have some limitations to sky, depending on location. Pointing at the sun is still bad And if it's in earth orbit, half the sky is blocked by the planet.
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  9. #8  
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    And not all telescope uses light to see (this mean that light distortion is not the entire issue), eg: gravitational-wave telescope need a very very quiet place to work (thus space is suited for such telescope). Some telescope need a total absent of atmosphere/earth to work (which meant space is absolute necessary), for example: a gamma ray telescope must be placed in outer space because our atmosphere blocked all the gamma rays. -So this kind of telescope need space to function and space is absolute necessary for them, so it doesn't matter how big the resolution it can get on the ground; what matter is that it get to space.
    Last edited by msafwan; October 16th, 2011 at 12:00 PM.
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  10. #9  
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    Quote Originally Posted by Jagella View Post
    Quote Originally Posted by Lynx_Fox View Post
    "Distortions"is probably too simple: ground based telescopes are blocked by theatmosphere and particulates from smog, clouds, and just the gasseswhich block, absorb and scatter a good part of the sky's EM spectrum.That we can only view half the sky from any one point is anotherproblem.

    I'm wondering how much of a problemsmog, clouds, and gases in the atmosphere are for telescopes in partsof the world in which the skies are relatively clear. Is there anyway to correct for blockages in the atmosphere?


    And what of the advantages ofground-based telescopes? They can be built with larger lenses withgreater magnification. Isn't that true? And they don't need to belaunched into space, of course, which isn't cheap, I'm sure.


    Thanks for pointing out thatground-based telescopes can only view half of the sky. Sometimes themost obvious things escape me.

    Jagella
    Much depends on wavelengths of spectrum desired to study. Lenses? Not so much, more like mirrors- Hubble had mirrors, for example. Easier to manufacture, lighter in weight, the former very important in space manufacturing, the latter not so much.

    More on a variation on a theme, possibly of interest:

    Liquid mirror telescopes - Wikipedia, the free encyclopedia
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  11. #10  
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    every telescope have its own limitations.....although it seems like space telescopes are obviously better than ground telescopes,i think both types are useful in different occasions
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    The bravest are surely those who have the clearest vision of what is before them, glory and danger alike, and yet notwithstanding go out to meet it.- Thucydides
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