File:‘Seeing’ atop Cerro Pachón (iotw2438c).tiff

English: The star-filled Milky Way arches over Cerro Pachón in this Image of the Week, the sky alight with the spectacular green, orange, and purple airglow of Earth's upper atmosphere. On the right is Gemini South, one half of the International Gemini Observatory, supported in part by the U.S. National Science Foundation and operated by NSF NOIRLab, while on the left atop the structure is the DIMM3 Seeing Monitor. Both Gemini South and the DIMM3 Seeing Monitor are perched at an altitude of 8980 feet (2737 meters) in the mountains of Chile. This high location is known for its dry, stable air, and provides the excellent ‘seeing’ conditions needed to make high-quality observations. However, even in the best conditions, the turbulent atmosphere will still distort the data. That’s where the DIMM3 Seeing Monitor (and the two other DIMM monitors at Cerro Pachón) come in. A Differential Image Motion Monitor (DIMM) is a small telescope that uses the characteristics of light waves to measure how much the atmosphere is distorting the stars above. This measurement is then used to sharpen other observations at other telescopes that were made at the same time, and help users of Gemini South and other telescopes on Cerro Pachón optimize their observations and use of valuable telescope time.You can find this photo in an original view here and in an extended view here.