Astroclimate

Astroclimate ( Astronomical climate ) - a set of atmospheric conditions that affect the quality of astronomical observations . The most important of them are the transparency of the air , the degree of its homogeneity (affecting the "sharpness" of the image of objects), the magnitude of the background glow of the atmosphere, daily temperature drops and wind power. In the optical range, the transparency of the Earth’s atmosphere is quite high: the light of a star at its zenith, when observed from sea level, is attenuated by 25-50% (weaker at the red, stronger at the blue end of the spectrum ), and from the height of a modern mountain observatory (2500- 3000 m) by an average of 20%. In the ultraviolet (UV) range, the transparency of the atmosphere decreases sharply: for waves shorter than 280 nm, it is practically opaque. In the infrared (IR) range, the transparency of the atmosphere is very heterogeneous: there are several powerful absorption bands by oxygen and water molecules. Therefore, for observation in the near IR range, telescopes are installed in dry high mountain regions, for example, in the Chilean desert of Atacama or on the peaks of ancient Hawaiian volcanoes (altitude more than 4000 m).