English: As the Sun sets and its light scatters through Earth’s atmosphere, the Arizona sky glows in wondrous shades of vivid color. Kitt Peak National Observatory (KPNO), a Program of NSF’s NOIRLab, is the perfect location to enjoy these spectacular sunsets. Arid deserts, like the Arizona-Sonoran Desert where KPNO is located, display a clearer array of colors than areas where rain and humid weather are almost daily features. When heavy particles are present in the atmosphere, like water vapor, they absorb some of the sunlight and desaturate the colors. Through dry desert air, however, sunlight can pass unobstructed as it reaches our eyes. These natural conditions are helped by the clean air and low air pollution that are due to Arizona’s sparse population. For astronomers, the torrid, cleaner air enhances their ability to capture sharper data of the visible sky once the dark sets in.This photo was taken as part of the recent NOIRLab 2022 Photo Expedition to all the NOIRLab sites.