A person walking rapidly through a heavy rainstorm with the drops falling straight downward, will have to tilt his umbrella slightly forward to compensate for his own motion. In the same way and for the same reason, an astronomer on a rapidly moving Earth must tilt his telescope slightly forward in the direction of the earth's motion in order to have the starlight fall exactly down the center of his tube. As a result of this motion, the apparent position of a star does not ordinarily coincide with its true position. We term this phenomenon the aberration or "wandering" of light. The maximum shift from true to apparent position is 20".47.from A Field Guide to the Stars and Planets by Donald H. Menzel
Like Shooting Stars (digital photograph)taken on the first Chicago snow of 2009
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