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Author
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Topic: Parallax of the Moon and High School Mathematics
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SMadden
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posted June 08, 2006 03:28 PM
Dear David,
I have an article coming out in the August Mathematics Teacher. The article describes how a series of activities can be done using simple tools available in the high school classroom. One of the activites involves using a homemade dioptra to measure the parallax of the moon over six hours thereby allowing a determination of its distance. Ptolemy did this first, of course. One of my reviewers suggested that the technique be generalized. As it is now, the technique, which I learned about from Abell's "Exploration of the Universe," is limited to the situation in which the Moon passes through the observer's zenith. Do you have a method of explaining how the measurement could be made and corrected for the situation in which the Moon and the reference body do not pass through the zenith? My reviewer's explanation is a bit difficult to follow. Perhaps you could send in your suggestion to the editor, too.
Take care,
Sean P. Madden
From: Greeley
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David Burch
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posted June 09, 2006 04:06 PM
This will take some thought.
One thing that comes to mind -- but I have no idea on the sensativity of the measurement -- is to do a simple (yet accurate) sun-moon or star-moon fix from a known position and experiment with changing the HP vlaue of the moon's sight reduction. HP is the horizontal parallax, which is effectively the distance to the moon, expressed as an angle.
From a known position, you may not need to do the second sight (since we are assuming the star sight goes exactly through your true position, anyway).
Just take a moon sight and then tweak the HP in the analysis until the line goes through your position. Then once you have HP and the known radius of the earth you can compute distance to the moon.
My guess is there would be a special bearing to the moon that would optimize the effect, but i do not offhand know what that might be.
From: Starpath, Seattle, WA
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