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I What shape is the ecliptic as seen from Earth?

  1. Sep 30, 2016 #1
    I want to build a model of how the ecliptic interacts with the horizon. The horizon appears to be a flat circle, so I thought I'd use a CD sized shape for that. What shape would I use for the ecliptic, and how large relative to the CD? I would like it to be as close as possible to the my horizon at all times of the day. I'm at 45 degrees lat.

    I tried with a circular ecliptic just a little larger that the horizon, but when I rotated the part that repented the ecliptic, it seem to hit the horizontal piece (the CD I'm using as the horizon).

    I thought this might be a geometry question of some type.
  2. jcsd
  3. Sep 30, 2016 #2


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    Staff: Mentor

    The ecliptic, as seen from the center of the CD, is also a circle. The size does not matter, if you want to move it around making the circle larger than the CD is advisable.
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