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 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 below the summit and to the southwest. This location has been given up due to the vicinity of the ELT construction site in January 2014. The Telescopes of the Bochum university, installed after 2006, are no longer operational. They are located further to the west and higher than the original OCA observatory, on a subsidiary peak of Cerro Armazones, Cerro Murphy. The coordinates here are those of this summit now.