From a recent visit to Cerro Tololo observatory in the Chilean Andes. The day begins with the valley below filling up with clouds from the nearby ocean about 40 miles to the west. The marine layer is caused by the cold Humbolt current which flows past the coast of Chile and which produces a climate similar to California. The air above the observatory is not super low humidity like it is further north in the higher elevations of the Atacama desert, but it is very very steady, and the seeing is superb.
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