Motion of the S13

Motion of the S13 - The declination of the Sun varies...

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Motion of the Sun Actually, the folks in the old days could figure out where the Sun would be relative to the stars by looking at the stars which were visible when the Sun set. They knew which constellations the Sun covered up and when they were covered up (which time of the year they were or were not visible). If you were to map out the path of the Sun relative to the stars, you would see it as a curved line on the Celestial Sphere. Take a look at Figure 1 to see the path relative to the Celestial Equator. This image is of a flattened out Celestial Sphere, and the dates mark the locations of the Sun relative to the stars over the course of the year. Figure 1. The path of the Sun, the ecliptic, shown relative to the background stars and the Celestial Equator (dec=0). The location of the Sun on the equinoxes and solstices is indicated. Some declination values are also indicated. As is apparent, the path of the Sun is curved relative to the Celestial Equator. There are times during the year when it is north of the Celestial Equator and other times when it is south of it.
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Unformatted text preview: The declination of the Sun varies throughout the year. (Of course, its R. A. changes as well, becoming slowly larger each day as the Sun moves eastward relative to the stars, but we'll pay more attention to the declination). On the days of the Equinoxes, the Sun is right on the Celestial Equator, so it has a declination of 0º, and on the Solstices, it has the most extreme value for its declination, 23.5º N on the date of the Summer Solstice and 23.5º S on the Winter Solstice. The Solstice dates mark when the Sun is at its greatest distance from the Celestial Equator. The path the Sun appears to make amongst the stars is known as the ecliptic . Just like the Celestial Equator, it would make a large circle on the Celestial Sphere. In fact the ecliptic is a big circle that is tilted 23.5º relative to the circle made by the Celestial equator. This is shown in Figure 2....
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