angular displacement diurnal aberration The component of the stellar abberation resulting from the diurnal motion of the observer around the centre of the Earth. The abberation is the apparent angular displacement of the observed position of a celestial object from its geometric position, caused by the finite velocity of light in combination with the motions of the observer and of the observed object. degree graad 度 microsecond (angle) microseconde (hoek) millisecond (angle) milliseconde (hoek) second (angle) seconde (hoek) 秒（角度）