The definition and understanding of Aberration

The definition and understanding of Aberration is a tilting of the apparent position of a star in the direction of the motion of the observer. The size of the effect depends on the velocity of the Earth, the velocity of the light, and the angle between the direction of observation and the direction of motion, with a maximum value of 20.47 seconds of arc.

The English astronomer James Bradley who lived between 1693 to 1762 discovered stellar aberration in 1728, proving that the Earth is not fixed in space, but moves through it, while also showing that light travels at a finite velocity, which he estimated as 308,300 kilometers per second using his observed value of aberration.

Source is: A Companion to Astronomy and Astrophysics, Chronology and Glossary with Data Tables, Kenneth R Lang, Springer 2006, Singapore.