Harquahala Smithsonian Observatory

GENERAL INFORMATION: Harquahala Peak Observatory was built in 1920 by the Smithsonian Astrophysical Observatory to measure and record solar activity. Although deserted now, from 1920-1925 a hardy group of scientists lived and worked atop the highest mountain in southwestern Arizona (5681 foot elevation). At the time, it was about an hour's drive from Wenden, Arizona, to the mountain, with a 3-hour hike to the top of the peak. Burros were used to pack building supplies, living supplies and equipment to the mountaintop. Most difficult of all to transport were the delicate recording machines and laboratory equipment. Even water had to be transported by burro until collection tanks could be built.

Harquahala was an observatory without telescopes. Rather, a theodolite was used for measuring the sun's altitude above the horizon. Pyrheliometers, mercury thermometers with shutters that opened or closed at set intervals to record heating and cooling, measured energy from both the sun's direct rays and scattered rays, and a pyranometer, an electric instrument, measured heat from the atmosphere around the sun. After tedious observation and data collection, the raw information was mathematically calculated by hand, sent to Washington, D.C., compared with data from another observatory, and used in forecasting weather.