Parallax is the apparent change in an object's viewing direction when the observer's position changes. Holding a finger in front of a distant background and alternately closing each eye gives a direct demonstration: the baseline is the separation between the eyes, and a nearer finger shifts farther relative to the background.
Stellar parallax uses the orbital baseline of Earth. Its conventional angle is half the maximum annual excursion for the full projected baseline. In the small-angle geometry, in radians, giving . For example, arcseconds implies parsecs. A real fit must also separate proper motion and aberration of light from this repeating geometric signal.
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Parallax is an effect that describes the apparent shift in the position of an object when viewed from different angles or perspectives. This phenomenon occurs because our viewpoint changes, allowing us to see different aspects of an object. In astronomy, parallax is used to determine the distance of stars and other celestial objects. By observing a star from two different points in Earth's orbit around the Sun (typically six months apart), astronomers can measure the angle of apparent shift against more distant background stars.