| An experience of almost 200 years in the process
of determination of the favorable conditions that exists in order to planned where to
install an astronomical observatory. This experience has been refined in the last 30 years
with the modern systems of evaluation sites. The considering factors for the selection of
the installation place of an astronomical observatory are of two type:
- Optical
- Mechanic
In the optical factor we consider;
- The quality of the image, well-known us 'seeing' in the astronomical slang, is
related to the variations displayed on an image caused by atmospheric alteration.
- Cintilation, is related to the total variations in the flow of the captured light
of a body.
- Extinction, consisting of the loss of light in a path by the atmosphere because
of absorption or dispersion.
- Brightness on the background the sky. Very important for the nightobservation,
mainly of weak bodies. This brightness is caused by dispersion of the light by celestial
objects, artificial light or atmospheric phenomena like the aurorae boreales.
In
the mechanical aspect the meteorological conditions that need to be taken into account
that affect directly or indirectly the instrumentation, such as:
- Wind affects causing vibrations of the telescope or turbulence.
- Temperature. In great elevations it mainly affects observers, although the sky is
more stable to low temperatures.
- Rank of day temperature. High variations of the temperature during the day is
negative for the optics of the instrument.
- Humidity. Excesses of environmental humidity cause condensation in the optics and
an malfuntion in mechanical operation, electrical and electronic parts.
- The previous conditions set the standard to choose to the most advisable places
for the installation of astronomical observatories. The mountains of great elevation
offerl:
- a) An elevation (regularly greater to 2000 meters above sea level) allows the
densest layers of the atmosphere stay under the level of the observatory.
- b) Distance from urban center.
- c) favorable Conditions of seeing, cintilation and extinction.
- The previous thing does not imply that all the mountains with elevation superior
to 2000 ms are favorable for observatories, since is considered in addition:
- The weather and microweather of the mountain: The mountains in tropical regions
present problems of high levels of humidity and few clear day/nights a year.
- The shape and location of the mountain: The isolated mountainous bulks not
conected with mountain ranges are more advisable that not caused convection and
turbulence.
- The logistic aspect: There are mountains that presents serious problems of access
and by consequence high costs of operation and maintenance of the observatories.
At
the end of the 1940's the and beginnings of the1950's, several American astronomers
struggled by the installation of a National Observatory for the United States where any
investigator could carry out his work having like condition only the quality of his
project.
The previous thing caused an extensive exploration in more than fifty mountains
in the United States and several countries. The final results allowed to determine the
existence of four regions in the world considered with optimal conditions for the
installation of astronomical observatories. These are:
- The mountains next to the Desert of Atacama, in Chile.
- Mountains in the Desert of Saudi Arabia.
- The extinct volcanos of Mauna Loa and Mauna Kea in Hawaii.
- The Sonora-Arizona Desert that extends in the northwest of Mexico and southwest
of the United States.
These regions had favorable weather conditions, the low humidity level, the
great amount of nights cleared to the year and the existence of several mountains with
elevations superior to the 2000 meters above the sea level.
These results caused the installation of the National Observatory of Kitt Peak,
90 km southwest of Tucson, Arizona, still considered the greater concentration of
telescopes in the world (21 at the moment), including the greater solar telescope of the
world, the McMath-Pierce, and the stellar telescope Mayall with a mirror of 4 meters of
diameter.
The same conditions have been taken advantage for the installation of other
observatories in Mount Bigelow, Mount Lemmon, Mount Hopkins and recently in Mount Graham.
At the moment there are 40 telescopes in the south of Arizona.
In Sonora, Mexico, in 1988 started operations the Astrophisic Observatory
'Guillermo Haro', with a 2.1 m telescope, operated by the National Institute of
Astrophysics, Optics and Electronics, INAOE, in the Mountain range of 'La Mariquita', 26
km from the city of Cananea.
INVEST IN THE FUTURE...
Last Update: January 22, 2000.
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