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Thread: The Sphere of Mars

  1. #1
    Join Date
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    The Sphere of Mars

    I hope this is not too stupid a question, I've been known to ask them sometimes...But...

    At Mars' closest approach, what magnification would be required to see the planet as an actual sphere as opposed to just seeing a very bright star-like object?

    I know that the math to figure this out is relatively easy...I just don't know what formula to use.

    Thanks in advance
    The facts, gentlemen, and nothing but the facts, for careful eyes are narrowly watching. Isaac Asimov

  2. #2
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    You may see it as a small disk, put for to appear as a sphere, Mars's reflection is too diffuse.
    You can play a little bit around with the JPL Solar System Simulator. I just don't know how to relate magnification to field of view, I guess, that depends on the scope.

  3. #3
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    Mars currently appears to be 22 arcseconds (0.0061 degrees) in diameter. The resolution limit of our eye is typically about 1 to 1.5 arcminutes (0.167 degrees). So the magnification needed should be approximately 1.5 arcminutes (90 arcseconds) divided by the current angular size.

    The result is that magnifications above 4x should show Mars as a nonstellar object.
    I have seen it as a disk in 15x binoculars, I can try with 10x binoculars and report back, if the clouds ever clear at night.

  4. #4
    Join Date
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    Quote Originally Posted by RichField
    The result is that magnifications above 4x should show Mars as a nonstellar object.
    Thanks Richfield...thats exactly what I was looking for.

    Quote Originally Posted by kucharek
    You may see it as a small disk, put for to appear as a sphere...
    Sorry, kucharek...I should have been more precise in my wording. I meant disk, not sphere.
    The facts, gentlemen, and nothing but the facts, for careful eyes are narrowly watching. Isaac Asimov

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