A planet's elongation is the angle between the planet and the sun as viewed by an observer from Earth. The concept of elongation was derived from Copernicus's model of the solar system. Copernicus lived in a time period where there were no telescopes. Saturn was the farthest planet that could be seen with the naked eye, so as far as Copernicus was concerned, it was the final planet in the solar system. Thus, the concept of elongation only applies to the "naked-eye" planets. To calculate the elongation of a planet, the observer must be able to see the planet and the sun at the same time. An ideal time to try this exercise is just before sunset or just after sunrise.
Instructions
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1
Research, either online or at your local library, the location of the planets in relation to the sun and the Earth on the day you choose to try the exercise. Determine which planets, if any, will be visible to the naked eye on that early morning or late evening.
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2
Go outside and look up at the sky. Locate the sun and the planet you wish to view.
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3
Hold a piece of paper up into the sky. Line up the flat edge of the paper with the sun and the planet.
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4
Draw a line pointing to the planet and another line to the sun. Use a protractor to measure the angle between the lines you drew for the planet's elongation.