1. Thanks Andy, Stellar Parallax is the best answer I think. 2. Stellar parallax remains the standard for calibrating other measurement methods.3. He then decided to experiment with applying photography to the determination of stellar parallax . 4. Stellar parallax remains the standard for calibrating other measurement methods ( see Cosmic distance ladder ).5. Since stellar parallax is only detectable with telescopes, his accurate speculation was unprovable at the time. 6. Bradley's discovery of the aberration of light was made while attempting to detect stellar parallax . 7. This led to the first successful measurement of a stellar parallax , though not to the first publication thereof. 8. His early work was focused on astrometrics, particularly in the examination of photographic plates to measure stellar parallax . 9. He met with opposition from astronomers, who doubted heliocentrism because of the absence of an observed stellar parallax . 10. Based upon stellar parallax measurements by the Hipparcos spacecraft, HD 147513 lies some 42 light years from the Sun.
