19.0315, -98.3151
Tonantzintla Observatory (Spanish: Observatorio de Tonantzintla) is an astronomical observatory located in the municipality of San Andrés Cholula in the Mexican state of Puebla. It consists of two adjacent facilities: the National Astrophysical Observatory of Tonantzintla (Spanish: Observatorio Astrofísico Nacional de Tonantzintla - OANTON), operated by the National Institute of Astrophysics, Optics and Electronics (INAOE), and the National Astronomical Observatory - Tonantzintla (Spanish: Observatorio Astronómico Nacional - Tonantzintla—OAN - Tonantzintla), operated by the National Autonomous University of Mexico (UNAM). OANTON is located on the INAOE campus, which includes numerous other buildings. OAN - Tonantzintla is located immediately to the east on mostly unused property. The observatory is located 11 kilometres (6.8 mi) west of Puebla and 33 kilometres (21 mi) east of Popocatépetl, eruptions of which sometimes interfere with observing.