The "El Leoncito" Astronomical Complex (Complejo Astronómico El Leoncito,CASLEO, in Spanish) was formally created in May 1983 as a National Service Center for the Astronomical Community. Its goals and functions include the maintenance, operation and management of the facilities run by the Complex, while providing astronomical observation services to investigators licensed to operate in the field, and performing other technical and scientific activities which might contribute to the development of the astronomical sciences. CASLEO was created within the National Scientific and Technical Research Council (CONICET in Spanish) with the participation of the National Science and Technology Secretariat and the National Universities of La Plata, Córdoba and San Juan. Its main instrument is a 215 cm in diameter reflecting telescope which was provided by the National University of La Plata and which has been named "Jorge Sahade", after the precursor of the initial idea which led to the creation of CASLEO. This telescope was purchased in the 60's and, in the following decade, the first steps were taken towards the acquisition of the 76,000 hectares which currently constitute an Astronomical and Ecological Reserve. It was at that time when the bidding specifications were prepared for the construction of the observatory facilities, and by 1983 when the formal agreement was signed for the creation of CASLEO, 40% of the necessary facilities had been completed.

The first Director of CASLEO took office in the same year, and the administrative, scientific and technical organization of the new observatory started. It was also the beginning of the hiring and training process of the personnel responsible for the provision of the service. The work was completed in 1985 and on September 12, 1986, the facilities were inaugurated. The President of the Argentine Republic, Dr. Raúl Alfonsín, attended the opening ceremony.

The Site

CASLEO is located in "El Leoncito", an area characterized by the very dark conditions of its night sky, with more than 250 nights a year of clear sky, no clouds, almost no wind blowing, and a typically diaphanous, contamination-free atmosphere. The water vapor content is also scarce.

"El Leoncito" is located in the Department of Calingasta in the Province of San Juan, 40 km away from the town of Barreal, facing a geological structure called "Barreal Blanco".

The main telescope is located 2552 m above sea level, in the western foothills of the Tontal mountain range, which separates the site from the valley where the city of San Juan (the capital of the Province) is located. Provincial Law 5771 protects the quality of the sky against potential man-made contamination and deterioration. In addition, since 1993, the Astronomical Reserve has been under the protection of the National Parks Administration, when a Strict Nature Reserve was created, followed by the creation of the El Leoncito National Park in 2002.


Working at an astronomical observatory is hard. The staff work in eight-day observing periods at a high altitude location. They have nonstandard work schedules, as the work is performed at night with winter temperatures reaching -10ÂșC. Therefore, it is necessary to be equipped with basic amenities necessary for every day life.


The facility can accommodate approximately 50 people. This number includes technical, administrative, maintenance, catering and cleaning staff, who are responsible for the work on the mountain, as well as researchers making use of their observing time. The facilities include double rooms with private bathroom, lunchroom, meeting room, and a recreational area for the staff. The observatory is also equipped with internet access, telephone communication system and TV.

Technical service is provided by high precision mechanical workshops, as well as metallurgy and vehicle service workshops; electronic, optical and IT laboratories, as well as other facilities necessary for the performance of the technical and astronomical work carried out.

The Complex also has its own power plant in order to avoid interruption of the work in case of power cuts in the commercial line. In the event of a power failure, a continuous power sytem will keep computers and other equipment in operation until the facility's own power generators start producing energy.

Over 2,000 square meters of construction have been completed. To date, the National Goverment has made an investment of over 20 million dollars.

The "Jorge Sahade" Telescope

This is the main telescope at the Complex. It was mounted between October and December 1984. Throughout 1985 and part of 1986 the electromechanical tuning of the equipment was carried out. In March 1987, the telescope started to be used systematically by astronomers in their research programs.

This instrument is a reflector telescope, with a 215 cm diameter primary mirror and a 65 cm diameter secondary mirror. With a total weight of 40 tons, it moves with the precision of a clock in order to compensate for the earth's rotation movement when tracking an astronomical object for observation. Its function is to collect the light from these objects and make it converge on a focus plane where it is analyzed by means of ancilliary instruments.

Among these instruments, there may be photometers for brightness measurements, spectrographs for chemical composition analysis and speed measurement, polarimeters for polarized light percentage measurement, or detectors for direct image.


Outreach Activities

CASLEO carries out an extensive program for the promotion of the astronomical sciences. Between 4,000 and 6,000 people visit the observatory facilities in Calingasta every year. Visitors are provided with information about the technical characteristics of the equipment and the work performed.

It is important to point out that the visit involves walking up and down stairs and the facilities at our Institute are not equipped to accommodate people with physical disabilities.

Daytime Visits to CASLEO

For daytime visits, visitors can simply come to our facilities on the mountain during the hours shown below:

  • 10:00 a 12:00 am and 2:30 to 5:00 pm, between April 1 and September 30.
  • 10:00 a 12:00 am and 3:00 to 5:30 pm, between October 1 and March 31.

Guided visits take around 30 to 40 minutes and include a tour of some observatory facilities, the visit of the "Jorge Sahade" telescope, and a short informative talk.

Night Visits to CASLEO

On certain nights every month the Institute receives a limited number of night visitors at its mountain facilities.

Visitors must arrange for their own transportation and may arrive at our facilities at around 5 p.m. A tour guide will welcome them and give them a tour of the facilities, including the "Jorge Sahade" telescope and other areas. During the visit, visitors are informed about the history of CASLEO, the work methodology, and the type of research carried out. This can take between 30 and 40 minutes.

Visitors are then shown to the lunch room for dinner. It should be pointed out that as CASLEO is a facility intended for scientific research involving work at high altitude, consumption of alcoholic beverages during meals is forbidden.

After dinner, if sky conditions permit, observing sessions are held with the assistance of our staff, involving viewing of celestial objects (the planets, the moon, double stars, galaxies, star clusters, etc.).

The observation plan is designed in advance by the observatory staff. It involves the use of a 35 cm diameter outdoor telescope. Therefore, it is advisable to bring warm clothes regardless of the time of year. The length of the visit may vary depending on the visitors' level of curiosity, as questions and comments may be made during the observation of the various astronomical objects.

Once the observing session has concluded, visitors either leave the observatory premises or stay overnight, depending on previously made arrangements. The town of Barreal, which is the closest to the facility, offers different types of accommodation, such as cottages, hotels, inns, at affordable prices.

NOTE: CASLEO is located at 2552 meters above sea level, which may pose a health hazard to some people. In addition, as scientific research is the main activity carried out, it is necessary to preserve the working conditions of professional astronomers visiting our facilities. Therefore, it is important to remember that:


For further information or questions about our promotional activities or visits, you can contact us at 0264-4213653 or 0264-4273653 or via e-mail to visitas@casleo.gov.ar.