Red Mountain Lookout Signal Mirror Flash

Signal Mirror Flashes at 14.4 mile range with 4"x5" glass signal mirror and "red dot" retroreflective aimer. From Red Mountain Lookout to Black Mountain Lookout in Riverside County, Southern California. Signal mirror flashes from an adjacent lookout are the best way to set the azimuth alignment on an Osborne Firefinder. Sun-mirror flashes from heliographs were used to communicate between fire lookout towers and the field from 1909 into the 1930s.
[1] Per "Handbook for Fire Lookouts", National Park Service, 1958, Ch.4 p. 7
npshistory.com/publications/ranger/fire-lookouts-handbook.pdf