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TUCSON- Rosemont Copper's proposed mining site would operate all night long. Heavy machinery calls for safety, and at night safety means light, and a lot of it. It's a concern brought to the attention of observatories in Southern Arizona who are working with Rosemont and the Forest Service to limit the glow as much as possible.

"You can imagine when the moon is up you see many fewer stars. That's what happens when you add light to the sky," explains Dr. Emilio Falco at the Whipple Observatory on Mt. Hopkins.

When light is added to the sky distant objects become faint, and they are often galaxies astronomers and star gazers are most interested in. For many big observatories the color of the light plays a big role as well. Gamma ray telescopes work by detecting blue light in the atmosphere. More light makes it more difficult to detect the blue. Rosemont Copper brought on Monrad Engineering to mitigate that problem.

"in the case of Rosemont we are actually not only choosing the most advantageous color for seeing color but we're using a filter on that that takes all the blue light out of the emissions," said Christian Monrad, Vice President of Monrad Engineering.

The company has overhauled the lighting project reducing lumens, a unit of light measurement, from 20 million to 6 million. LED technology has helped significantly, and strategy has changed as well.

"It's much easier to reduce off site glare, light trespass and sky glow when you use the light much like a paintbrush," said, Monrad.

The fear by observatories is that this pattern of added light could significantly reduce a billion dollar industry in Southern Arizona.

"that will limit our current studies and it may limit the future because funding agencies will see there is all this light in the sky, it's not worth bringing new telescopes or instruments to Mt. Hopkins."

Dr. Emilio Falco is working with the Forest Service and Rosemont to develop the environmental impact statement. He wants to be sure light will be monitored to limit the glow and he wants to be sure that limit is strongly enforced. Rosemont Copper still has to get all of the proper permits in place to move forward.