In most situations, light helps us see. But when it comes to looking at the night sky, light is actually a kind of pollution. Normally, about 2,500 individual stars are visible to the human eye without using any special equipment. But because of light pollution, you actually see fewer than a dozen from a typical city.
Viewing of stars with the naked eye has reduced about three to four times in the last few years due to increased light and air pollution. Earlier, star gazers had to travel about 20-25 kms from the city to find a starlit sky to gaze. Now they have to travel about 40-60 kms.
A few years ago, stars of five magnitude were visible from some parts of the city, but now, stars with less than four magnitude are seen, which means less brighter stars are not visible any more. The increased pollution levels have created a barrier between the observer and the sky. Light pollution is one factor, while pollutants in the air are another factor affecting visibility.
Heavy flood lights in the city are mainly responsible for light pollution as the high capacity light gets scattered in the sky. These lights should have a shade to prevent light from spreading upward which is a waste and the unwanted lights put up just for decoration should be reduced. Because of this artificial lighting, a starlit sky is becoming rarer in the city. Development around the city is also limiting the visibility of stars.
