Little Points of Light
The article discusses several approaches in determining the spectroscopic aspects of the stars and the galaxy formulated by various astronomer. It notes that astronomer Norman Robert Pogson created a magnitude system to analyzes the perceived brightness of the stars by differentiating between the apparent magnitude and the absolute magnitude. It mentions on the development of the Hubble's law by astronomer Edwin Hubble and Milton Humason to determine the spectra of a collection of galaxies.
Ball, David W., "Little Points of Light" (2011). Chemistry Faculty Publications. 152.