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Astronomers use the parallax method because it is one of the most accurate and straightforward ways to measure the distance to stars. Astronomers measure the position of a star once and then again 6 months later and they compare the two measurements to find the apparent change in angle, which is the parallax angle. This happens because during the course of those 6 months, the Earth has moved as far away from the point of original measurement as possible, and therefore the apparent change in angle is the largest possible and which makes it easy to measure. Now astronomers possess and develop new instruments that can measure very tiny angles (very small fractions of an arcsecond) so the measurement of the distance becomes much more accurate using this method. After finding the parallax angle, it is a question of simple trigonometry to determine the distance of the star from the Earth.