aberration of starlight

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Apparent displacement of a star from its true position, due to the combined effects of the speed of light and the speed of the Earth in orbit around the Sun (about 30 kps/18.5 mps).

During a year the apparent position of a star describes a curve around its true position. This curve is an ellipse except when the star lies on the ecliptic (when it is a line along which the star appears to move backwards and forwards) or when it is in the pole of the ecliptic (when it is a circle). As aberration depends upon the ratio between the velocity of light and the velocity of the Earth, the determination of this ‘constant of aberration’ provides a method of calculating an approximate value for one of these velocities if the other is known.

Red, white, and blue are the pan-Slav colours. The small shields represent Croatia Ancient, Dubrovnik, Dalmatia, Istria, and Slavonia. The flag is based on the tricolour used during World War II. Effective date: 22 December 1990. >>