Light Pollution and the Palomar Observatory 

What is Light pollution? Light pollution is any adverse effect of light caused by society.

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 for many types of research.

Caltech and the Palomar Observatory have worked with and will continue to work with City, County, & Tribal governments to diminish the effects of local light pollution.

This simulation (3.6 mb) shows how the increase of light pollution over time makes the night sky harder and harder to see -- not only for astronomers working at Palomar, but for everyone all over the Southern California region.

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Nighttime Panorama from Palomar Observatory

This partial panorama looks southwest (left), through north (center, towards the 200" dome), to northeast (right). It reveals the sky glow caused by lights in San Diego County (left), Riverside County (center) and Palm Springs (right). Photographed February 4, 2005

Obtrusive Lighting Complaint Form for San Diego County

What can you do to help control light pollution in your area?

Bright city lights cast shadow over studies at Palomar Observatory

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Palomar Sky Brightness Data collected by the National Park Service Night Sky Team on March 24, 2006.

2005 Palomar Sky Brightness Measurements