Cerro Armazones Observatory (Spanish: Observatorio Cerro Armazones, OCA; German: Observatorium Cerro Armazones, OCA) was an astronomical observatory owned and operated jointly by the Ruhr University Bochum (RUB) and the Catholic University of the North (UCN). It was established in 1995 on the slopes of Cerro Armazones, a mountain in the Antofagasta Region of Chile. The observatory is located in the Atacama Desert about 110 kilometres (68 mi) south of the city of Antofagasta. Unlike many other observatories, OCA is not located at the highest point of its host mountain. Instead, it was in a saddle approximately 340 metres (1,120 ft) below the summit and 1 kilometre (0.62 mi) to the southwest. This location has been given up due to the vicinity of the ELT construction site in January 2014. Th