Dr. Dennis Crabtree by RoyalBCMuseum published on 2018-06-19T23:24:28Z Dr. Dennis Crabtree, director of optical astronomy at the Dominion Astrophysical Observatory, speaks about a day in the life of a typical astronomer 100 years ago. He explains how astronomers used photographic plates to obtain spectrums of stars (properties of light that radiates from stars). This information could be used to calculate the radial velocity (the speed at which a star moves away from or toward us). Read more about J.S. Plaskett, the first director of the Dominion Astrophysical Observatory.