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Sunset Anomaly (Posted on 2016-03-09) Difficulty: 2 of 5
The cover of the June, 1979, issue of Sky and Telescope magazine had a 38-minute time exposure photo showing the setting sun over Boston harbor. It was taken on September 25, 1973, three days after the equinox.

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As the sun is then south of the equator, the sun's path in the sky should be an arc of a lesser circle (as opposed to a great circle, which would appear as a straight line on a photograph) centered on the south celestial pole, which is below the horizon, to the left (south). As a result, the concave side of the path should be toward the bottom/left. However the picture shows its concave side is on the top/right, toward the north celestial pole. What happened?

  Submitted by Charlie    
Rating: 3.0000 (1 votes)
Solution: (Hide)
When the sun is over 7° up in the sky, the earth's atmosphere doesn't have much of an effect on the position of a celestial body, but as the body (the sun in this instance) approaches the horizon, atmospheric refraction makes the body appear slightly higher in the sky, the effect reaching its maximum of about 1/2° when the body reaches the horizon. At just three days past the equinox, this bending of the lower portion of the path was sufficient to overcome the spherical geometric curvature in the other direction.

Comments: ( You must be logged in to post comments.)
  Subject Author Date
I feararmando2016-03-14 15:41:18
Thoughtsarmando2016-03-11 15:17:45
HiEzequiel havelles2016-03-10 00:54:55
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