The problem of light pollution in our towns and cities is generally a question of quality not quantity. It is poor quality light that causes this pollution effect and is a problem that can be discussed in terms of direction and efficiency. Armagh Observatory recently described four different types of "poor lighting" that increases light pollution.

  1.  Light Trespass—poorly directed security lights shining out of their designated areas.

  2.  Sky Glow—projection of light directly onto the sky by unshielded and poorly directed lights.

  3.  Glare—the direct dazzling effect of bright lights.

  4.  Light waste—areas illuminated when nobody is present.

  All these problems combine to create massive energy waste, security problems and a reduction in visibility of the night sky. This reduction is detrimental to both professional astronomers (noticeable from the lack of major UK based astronomy projects) and amateurs alike.

  It is obvious that the cost of upgrading and replacing all of these pollutant lights would itself be "astronomical". It would, however, be far less costly, and more cost effective in the long run, to lay down some "dark skies" guidelines today in order to reduce light pollution in the future. La Palma (Spain), Flagstaff (Arizona) and Bisei (Japan) already have a "dark-skies" policy and these places are now enjoying the environmental, economic and social benefits of their respective schemes.

  A darker sky may not change the world but it will help us to look upon whole new worlds from our back gardens.

29 April 2003