Once the parallax angle has been established then the distance of the star from the earth’s surface can be established. Due to this notion then the smaller the parallax shift then the further a star is from the earth’s surface. The use of parallax is useful in measuring the distance of stars that are within a range of few hundreds of light-years from the earth.
The units that we use to measure the distance from the earth’s surface to different stars is either in the form of light years, parsecs, or Astronomical Units (AU).
The use of the parallax method of measurement of distance of stars from the earth’s surface has its own limitations. In the first place the method can only be used to measure the distance of stars that are within a certain range from the earths’ surface. In these cases where parallax is no longer applicable astronomers use Cepheid variable stars to measure the distance of distant stars. According to astronomers these stars change in their brightness that allows them to determine their true brightness over time. By comparing the true brightness of the star to its apparent brightness astronomers can determine or calculate the true distance of the specific star.