An Observatory

1. A place where stars, planets and other celestial bodies are observed, usually through a telescope; also place for observing meteorological or other natural phenomena.
2. A lookout (vantage point with a view of the surrounding area)

Astrophysics:

Ground-based Observing

The considerable investment in large telescopes and sophisticated equipment requires more regular utilization of the facilities. Moreover, high quality telescopes are built at the sites that best allow them to take advantage of their capabilities. Observatories are built only after there has been an extensive investigation of the quality of the site. Instruments have become more expensive.

The selection of an observatory site depends on a number of considerations.

• Weather: clear weather is important, but not enough. The air should be dry, since water vapor can attenuate signals. This suggests a desert.
• Altitude: the higher the telescopes is, the less air to look through. This suggests a mountain. Even with a mountain in the desert, good seeing is not guaranteed.
• Local Conditions: Seeing often varies depending on air flow and terrain.
• Light Pollution: Light from nearby cities is reflected up into the sky, making the sky appear to glow. The brighter this glow, the harder it is to see faint astronomical objects. Certain lights can be tackled by adding filters and hoods.

Observations from Space:

This is particularly important for observing in parts of the spectrum that don’t penetrate the Earth’s atmosphere. However, a telescope in space can even be important in the visible part of the spectrum. It makes observations free of the blurring caused by atmospheric seeing conditions.