Lightscape / Night Sky
What are the boundaries of Big Bend National Park? Most of us would reply in lateral terms, defining the “ground level” boundaries of the park. Yet what about the park’s vertical boundary?
We cannot define an upper limit to Big Bend National Park. Panoramic views of the horizon extend for almost 250 miles on a clear day, but on a clear night we can see as far as 2 million light years away to the Andromeda galaxy! (Converted to miles, that’s 13.2 x 10 to the 17th power or 13,200,000,000,000,000,000 miles.) At night we look back in time as well as across space. When we see the reddish star Antares in the constellation of Scorpio (visible before dawn in winter and spring), we’re looking at light that takes 500 years to reach us.
Several factors make Big Bend an excellent place for night sky-watching. The absence of light pollution, so prevalent near developed areas, makes this area unique among most viewing areas. Big Bend's infrequent cloud cover and low humidity, especially in winter, allow for sharp visual acuity.
Casual observation and detailed study show that winter skies in Big Bend are the cleanest, compared to air quality at other times of the year. A great deal of air pollution blows into the park from sources in Mexico and other parts of the U.S. in the summer, but northerly winter winds bring much less debris. One more attribute to winter sky-gazing in Big Bend: the nights are longer than the days, so take advantage of them!
For city-dwellers accustomed to seeing only a handful of stars, Big Bend’s star-laden skies can be dazzling and a little intimidating. On the clearest nights, around 2,000 stars are visible to the naked eye here. Add a few planets and some “shooting stars”, or meteorites, and you’ve got a nocturnal display that’s well worth the cold weather! You don’t need a telescope to observe the night sky, although some people use binoculars.
Recently, Big Bend earned the distinction as the park with the least light pollution in the lower 48 states. As it becomes increasingly difficult to find places free of air pollution and light interference, places with dark, clear night skies become that much more valuable. The noted Englishman Havelock Ellis said, “The moon and stars would have disappeared long ago had they been within the reach of human hands.” Though they still remain far from our reach, we are indeed losing sight of the stars through the work of our own hands.
For More Information
NPS Natural Lightscapes program
Did You Know?
Near the north entrance to Big Bend National Park, Dog Canyon cuts through the Santiago Mountains. Although the real source of the canyon's name is unknown, it was called "Cañon del Perro" by the Spaniards in the late 1700s and early 1800s. More...