Parallax error is the displacement or difference in the apparent position of an object viewed along two different lines of sight. It is most commonly encountered when measuring the distance to a celestial body, such as a star or planet.
Parallax error can be a significant source of error in astronomical measurements, so it is important to take steps to avoid it. There are a number of ways to do this, including using a parallax barrier, which is a device that blocks the view of the object from one eye.
