Sir

Your editorial “Save starry nights” (Nature 418, 709; 200210.1038/418709b) states that Czechoslovakia is the only country with a national policy aimed at limiting light pollution. In fact, Chile, which now contains the largest concentration of optical telescope aperture* in the world, has taken a similar step.

The Association of Universities for Research in Astronomy, the European Southern Observatory and the Carnegie Institution worked for several years with the major Chilean universities and local and national government authorities to implement a strategy for controlling light pollution.

In December 1998, then-President Eduardo Frei signed a decree to establish an environmental norm regulating all outdoor lighting, not only in the areas surrounding the existing observatories, but in all of the II, III, and IV Regions of northern Chile, one-third of the total area of the country. The decree states in part: “The astronomical quality of the skies of the II, III and IV regions of our country constitute a valuable environmental and cultural patrimony recognized internationally as the best existing in the Southern Hemisphere for astronomical observations.”

The projected savings in energy costs from replacing polluting lights with well-shielded, energy-efficient ones should more than pay for the initial investment required for the changeover.

* corrected since original publication.