Who collaborated with Hubble to measure galaxy redshifts at Mount Wilson?

Milton Humason collaborated with Edwin Hubble to measure galaxy redshifts at Mount Wilson Observatory. Humason's observations supplied crucial information about how fast distant galaxies appeared to be receding.

Humason had an unusual path into astronomy. He began working at Mount Wilson as a mule driver and later became a janitor and night assistant before developing expertise as an observer and photographic spectroscopist. His ability to obtain spectra from extremely faint galaxies made him an important partner in Hubble's work.

Hubble primarily used observations of Cepheid variables and other methods to estimate galaxy distances, while Humason measured spectral shifts that indicated recession velocities. Combining the two data sets revealed the approximate linear relationship now called Hubble's law. Their later work in the early 1930s strengthened the evidence for cosmic expansion.

Vesto Slipher is a common alternative answer because he measured many important galaxy redshifts at Lowell Observatory and provided data that influenced Hubble's research. However, the question specifies collaboration at Mount Wilson, where Milton Humason was Hubble's key observing colleague. Henrietta Leavitt contributed foundational Cepheid-period research, but she did not perform this Mount Wilson redshift collaboration.