Question: John Henry Reynolds was a British astronomer who served as the president of the Royal Astronomical Society who frequently corresponded with American astronomer Edwin Hubble, developed a formula for measuring the surface brightness of what? 
Sentence (from "John Reynolds (astronomer)"): Images from the Reynolds telescope was later used by Gérard de Vaucouleurs in his system of classifying galaxies; Reynolds also published his own classification for spiral galaxies in 1920.
Relevant evidence: No