The place reminds you of pictures of proposed space colonies but there is one difference. Every attempt is made at nighttime to prevent any leaking of light from the roof or the walls of this underground building to the outside world. As if to underscore this fact, a huge umbrella opens out under the circular roof after sunset.

At nightfall this light curfew extends rigidly to the outside world also. No buildings in the campus have lights outside. Even driving between the residency and the telescopes has to be done in cars with no headlights on. It can be a scary experience for the novice, for the roads are hilly, winding and without streetlights.

Why such stringent precautions for preserving darkness? Because for using the telescopes in the most effective way, the observer likes to have the sky as dark as possible. Even the presence of the moon can be distracting as it reflects and scatters light from the sun and brightens the sky. The poet may admire the moonlit sky but the astronomer would consider the moon an agent for pollution. Indeed, when allotting observing nights to different astronomical proposals, the telescope committees give nights with less moonlight to observations looking for very faint objects.

Astronomers have increasingly faced the problem of light pollution over the last five decades. As urban populations grow and expand geographically, the night sky gets brighter and brighter with light from streets, buildings, hoardings and transport. This makes it more and more difficult for the astronomers to carry out their observations. Amateur astronomy groups from cities have to plan excursions well outside their cities to find dark enough areas for their night sky watches. This problem is faced by professionals too. Thus, telescopes at the once famous observatories like Mount Wilson or Kitt Peak have been rendered less and less effective and useless. Deserts and high mountain peaks like in Chile and Hawaii, are the havens where astronomers are forced to site their best telescopes.

... contd.