Monday, August 28, 2017

Moon Motion Relative to the Earth-Sun Line


  I was looking at the Moon's motion relative to the line through the centers of the Earth and the Sun and found what appears to be a Lissajous curve for the direction Moon.


This track has a three dimensional structure.


This plot of the focus and point of view shows the observer's relative position to the Moon's orbit.


The colors of the eye positions indicate the color of the lenses for the 3D glasses. The corresponding curves have the opposite colors since they are blocked by a lens so the eye will see a black line with the proper relative position.

Edit (Aug 28): Corrected the horizontal axis label in the 3D image.

Supplemental (Aug 28): Here's another view with a large black dot showing the relative position of the Moon for noon on the day of the eclipse. Remember there's a change of scale for the vertical axis. Note the Moon's orbit is inclined relative to the ecliptic by about 5 degrees and the sine of 5 degrees is about 0.087.


The Moon appears to have been below the ecliptic on the day of the eclipse.

Supplemental (Aug 29): I was concerned by the relatively low position of the Moon position on the plot for the day of the Aug eclipse but we are viewing the Moon's orbit from the plane of the ecliptic. Viewing from below the ecliptic and bring the Moon closer to the Earth-Sun line.


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