Félix Aguilar Observatory ( ; OAFA) is an astronomical observatory. It was established in 1953, in San Juan Province, Argentina. In 1974, it was renamed to Carlos Ulrrico Cesco Astronomical Station ( ; EACUC). Its primary observing facility is located El Leoncito National Park in the west of San Juan Province. Also located in El Leoncito Park is the Leoncito Astronomical Complex. The observatory is operated by the School of Physical and Natural Sciences at National University of San Juan in San Juan, Argentina. The original OAFA observatory buildings are located at the west end of the city. OAFA is named after Félix Aguilar (1884–1943), an Argentine astronomer and engineer who was director of the La Plata Astronomical Observatory from 1919 to 1921, and again from 1934 until his death. EACUC was renamed after Carlos Ulrrico Cesco on the 25th anniversary of the beginning of observations in honour of his contributions to the founding and operation of the observatory. The main-belt asteroid 3083 OAFA, was named after the discovering Felix Aguilar Observatory. The official naming citation was published on 21 November 1991 (). History In 1947, research had been started at the Lick Observatory in California to study the Northern Milky Way's structure by determining the accurate positions and apparent motions of stars. There was a need to extend that investigation to the Southern Hemisphere, and in 1960, Yale University obtained initial funding of 750 k$ for the purpose of building a southern observatory for that purpose from the Ford Foundation. Following a survey of potential sites, the observatory was built at El Leoncito, Argentina, near Barreal in the province of San Juan, in the eastern foothills of the Andes mountains at an elevation of approximately 2400 m (8000 ft). The site was provided under a long-term lease by the University of Cuyo and the observatory was jointly operated by the University of Cuyo's Observatorio Astronómico "Félix Aguilar" (OAFA) in San Juan and the Yale-Columbia Southern Observatory, Inc (YCSO). A residence was constructed adjacent to the grounds of the OAFA in San Juan for the technical support and housing of the YCSO personnel while they were in San Juan. The first survey of the Southern sky was made between the years 1965 and 1974, with the financial support of the National Science Foundation (NSF). During that period, the US Naval Observatory (USNO) relocated a meridian circle telescope to El Leoncito