Allan Sandage is an american astronomer that has undertaken extensive efforts to evaluate Hubble's constant rate of universe expansion.
in the beginning of his career in 1958 , the primary focus of Allan is to evaluate the Hubble's constant rate.
He used many different techniques to determine the distance to several galaxies. From these many different calculations, average value of Hubble's constant was about 50 km/sec/megaparsec.
