The Bortle scale is a nine-level numeric scale that measures the night sky’s brightness of a particular location. It quantifies the astronomical observability of celestial objects and the interference caused by light pollution. John E. Bortle created the scale and published it in the February 2001 edition of Sky & Telescope magazine to help amateur astronomers evaluate the darkness of an observing site, and secondarily, to compare the darkness of observing sites. The scale ranges from Class 1, the darkest skies available on Earth, through Class 9, inner-city skies.
Until recently, for all of human history, our ancestors experienced a sky brimming with stars – a night sky that inspired science, religion, philosophy, literature and art. Unfortunately, we’ll never know the great art we’ve lost to light pollution.
Enjoy these beautiful pieces of art inspired by starry night skies and learn how you can help inspire future generation to invent, create and dream.
Astronomers predict that Comet ISON, which will be at its brightest in late November, may put on the most impressive sky show of the century. Some of the country’s darkest skies — the best places to see ISON and other spectacular starry sights — may be just a few hours’ drive from where you live.
Anza-Borrego Desert State Park, California
It’s a two-hour drive east from the bright lights of San Diego, but the skies can get so dark at this desert outpost that you can occasionally see the northern lights. Stargazers come by the thousands, but if you prefer a more private show, the Borrego Valley Inn has intimate patios for night-sky viewing. [image]
Cherry Springs State Park, Pennsylvania
The only spot in the East awarded a gold rating by the International Dark Sky Association is this 2,300-foot-high mountaintop 180 miles northeast of Pittsburgh. A dimly lit sky map tells what you’re seeing. Related: this post. [image]
Kitt Peak National Observatory, Tucson, Ariz.
How dark are the skies over Kitt Peak? There may be more telescopes here (27 of them) than anyplace else on the planet. Day tours are popular, but for a real star-studded experience, sign up for a nightly tour. [image]
In the still, dry air of Tonopah — 200 miles from the lights of Las Vegas — you’ll stand beneath a blanket of more than 7,000 stars. The Tonopah Astronomical Society sponsors monthly star parties at Highland Park. [image]
Green Bank, W.Va.
The world’s largest steerable telescope — a 485-foot-tall, 17-million-pound behemoth — provides the backdrop for stargazing at the National Radio Astronomy Observatory (adults: $6). Sheltered from light by a valley, it stands within a day’s drive of the East Coast megalopolis. Come for a tour (hours vary by season) or for special events; last year there was dancing under the stars. [image]
Baxter State Park, Maine
Many dark-sky enthusiasts think you have to head west for good viewing, but this park ($14 per vehicle; baxterstateparkauthority.com/index.htm), less than 50 miles west of I-95, reveals the Milky Way and its friends in breathtaking clarity. Besides the inky black firmament, you’ll also enjoy a cellphone blackout — here where the roads are gravel, the only connectivity you’ll find is with the occasional moose. [image]