It can be thought of as a camera, where glass photographic plates 14 inches square are needed to record the image. The resulting photographic sky atlas will constitute a basic source of astronomical information for researchers throughout the world. Much of the light radiated by the stars, galaxies, and quasars is at wavelengths that are absorbed by the atmosphere of the Earth. To collect this light, astronomers are now able to operate highly specialized telescopes that orbit the Earth above the atmosphere. The relationship between these space telescopes and those at ground-based observatories like Palomar is complementary.
Light pollution is an increasing problem for observatories everywhere.
One of the reasons Palomar Mountain was selected as the site for the 200-inch telescope was its dark skies that would allow observation of the faintest galaxies without the interference of city lights. Since 1934, rapid urbanization of southern California has resulted in a significant increase in the amount of sky glow. If such light pollution continues to increase, it will seriously reduce the effectiveness of the Palomar Observatory. Fortunately, steps can be taken to minimize those effects. Shielding lights to prevent any direct upward illumination.