Undulatus Clouds over Las Campanas ObservatoryWhat’s happening with these clouds? While it may seem that these long and thin clouds are pointing toward the top of a hill, and that maybe a world-famous observatory is located there, only part of that is true. In terms of clouds, the formation is a chance superposition of impressively periodic undulating air currents in Earth’s lower atmosphere. Undulatus, a type of Asperitas cloud, form at the peaks where the air is cool enough to cause the condensation of opaque water droplets. The wide-angle nature of the panorama creates the illusion that the clouds converge over the hill. In terms of land, there really is a world-famous observatory at the top of that peak: the Carnegie Science’s Las Campanas Observatory in the Atacama Desert of Chile. The two telescope domes visible are the 6.5-meter Magellan Telescopes. The featured coincidental vista was a surprise but was captured by the phone of a quick-thinking photographer in late September. Your Sky Surprise: What picture did APOD feature on your birthday? (post 1995)