The Palomar Lights (opens in new tab)

Palomar Mountain, California\. November 1949\. Five thousand feet above the orange groves and the Navy airfields of San Diego County, the most ambitious map of the sky ever attempted is about to begin\. George Abell is a graduate student\. From this observatory he will discover 2,712 galaxy clusters\. But tonight, he just needs clear skies\. George is mapping a patch of sky\. Each patch is photographed twice — once on a red-sensitive plate \(fifty minutes\), once on a blue plate \(te...