Cerro Armazones Observatory (Spanish: Observatorio Cerro Armazones, OCA; German: Observatorium Cerro Armazones, OCA) is an astronomicalobservatory 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. The Telescopes of the Bochum university, installed after 2006, are still fully operational, and are located 500 metres (1,600 ft) further to the west and 100 metres (330 ft) higher than the original OCA observatory, on a subsidiary peak of Cerro Armazones, Cerro Murphy. The coordinates here are those of this summit now.
On 26 April 2010, the European Southern Observatory Council selected Cerro Armazones as the site for the planned European Extremely Large Telescope. The telescope will be located at the summit of the mountain at an altitude of 3,060 metres (10,040 ft). Currently the mountain top is flattened for this prupose and a new access road has been built.
The 1.5-metre (59 in) Hexapod-Telescope reflector is named for its unusual mount, consisting of six high-precision struts supporting a platform to which the telescope is attached. It was developed and tested by RUB in Germany, and moved to Cerro Armazones in 2006.
A 0.84-metre (33 in) Newtonian telescope made by Halfmann Teleskoptechnik was installed by UCN in 1995.  It has been dismounted in the meanwhile due to the vicinity to the ELT construction site and is currently at ESO Paranal for refurbishing.
A 0.41-metre (16 in) reflector made by Meade Instruments is owned by UCN. It has been dismounted in the meanwhile due to the vicinity to the ELT construction site and is currently at UCN doentown in Antofagasta to be installed in a new dome near Sirius in the campus for public activities.
^Kabath, P.; Fruth, T.; Rauer, H.; Erikson, A.; Murphy, M. G.; Chini, R.; Lemke, R.; Csizmadia, Sz.; Eigmüller, P. et al. (2009). "CHARACTERIZATION OF CoRoT TARGET FIELDS WITH BERLIN EXOPLANET SEARCH TELESCOPE. II. IDENTIFICATION OF PERIODIC VARIABLE STARS IN THE LRc2 FIELD". The Astronomical Journal137 (4): 3911. arXiv:0903.0325. Bibcode:2009AJ....137.3911K. doi:10.1088/0004-6256/137/4/3911.