Several of the larger concentrations of professional telescopes are high up in the mountains of Arizona. The high altitudes of the mountains reduce the amount of atmosphere required to view through, while the dryness of the Arizona countryside allows for the maximum number of days for viewing. Light pollution Light pollution reduces how dim any astronomical object can be. Man made light pollution is becoming a major problem to the amateur and professional astronomer alike. As cities become larger, more light is radiated into the night time sky.
Light domes over cities are now all too common place, making dark sky sites very hard to find.
Air pollution is also a major problem. The small particles found in air pollution tend to distort the light from deep sky objects as the light passes through the atmosphere. What little color is present, is now distorted. Many astronomers now have to drive several hours to get to a dark sky location, free from light and air pollution. Aperture The telescope's aperture size is directly proportional to how much light is need for you to see an object.