In September 1966, an AF C-130 aircraft, instrumented with Visibility Laboratory optical and meteorological sensors, was flown along a path of sight from a camera on Pikes Peak to a target array near Castle Rock, Colorado. The beam transmittance for the path of sight was 0.238, the universal contrast transmittance was 0.161, and the path luminance was 2062 cd m-2. A second data gathering descent was made from 9800 m, over the target array toward the southeast to an altitude of 1700 m. Beam transmittance for vertical path of sight for total atmosphere was 0.686. Atmospheric optical data presented include additional beam transmittances, attenuation length, background luminance, equilibrium luminance, horizontal path function, illuminances, and terrain reflectance.
Almerian R. Boileau, "Atmospheric Optical Measurements in Central Colorado in Connection with Long Range Oblique Photography," Appl. Opt. 7, 407-414 (1968)