Reference

Allan Sandage's 1961 paper, titled "The Ability of the 200-inch Telescope to Discriminate Between Selected World Models," had a profound impact on observational cosmology. This seminal work greatly influenced the field for several decades.

Sandage's paper was instrumental in advancing the understanding of the universe's structure and expanding the methodologies used in observational cosmology. It laid the foundation for modern observational techniques, allowing astronomers to better discriminate between different cosmic models using powerful telescopes, such as the 200-inch Hale Telescope at Palomar Observatory.

His research marked a significant turning point as it refined the methods used to gauge and understand the universe's expansion, contributing critical insights that fed into the determination of cosmic parameters like the Hubble constant. Sandage's work also spurred the use of quasars in studying distant universes, despite him initially struggling to correctly interpret their spectra.

For a detailed read, you can access more information here: NY Times article on Allan Sandage and source from the Royal Society.