Bortle Scale & Light Pollution Guide - Dark Sky Finder USA
Learn how the Bortle scale measures light pollution, find over 100 certified dark sky parks near you, and check tonight's stargazing conditions across all 50 states.
Enter a ZIP code, place name, or click the map to find dark sky sites near you. Over 100 certified International Dark Sky Places are plotted on the map, from parks and sanctuaries to reserves and communities. The Bortle scale, explained below, is the standard way astronomers rate night-sky darkness from a pristine Class 1 to an inner-city Class 9. The moon phase widget shows whether tonight is good for stargazing, calculated in your browser. Looking up a ZIP code sends it to Zippopotam; a place name is looked up against our own local data. Clicking the map sends those coordinates to OpenStreetMap's Nominatim to find the place name, the only thing sent out. None of it is stored by MapTools.
Light Pollution in the USA, and How to Find Dark Skies
Light pollution is measured on the Bortle scale, a nine-level standard running from Class 1 (pristine dark sky) to Class 9 (inner-city sky) - see the full breakdown below. Enter a ZIP code, type a city name, or click anywhere on the map to find the nearest dark sky sites ranked by distance, and use the Bortle reference to gauge roughly how dark your own sky is likely to be.
This tool shows over 100 certified International Dark Sky Places plotted on the map so you can find stargazing locations near you. The moon phase widget tells you whether tonight is good for stargazing, and you can share your location with a direct link.
The Bortle Scale, Explained
The Bortle Dark-Sky Scale was created by amateur astronomer John Bortle in 2001 to measure night sky brightness on a 1 to 9 scale. It's the standard reference for describing how dark a sky actually is, from a pristine Class 1 to a washed-out inner-city Class 9.
Most US cities are Bortle 7 to 9 -you will only see the Moon, planets, and a handful of bright stars. Suburban areas are typically Bortle 5 to 6 -some constellations are visible but the Milky Way is washed out. To see the Milky Way clearly, you need Bortle 4 or darker. The darkest locations in the US, including parts of Nevada, Utah, New Mexico, and central Idaho, can reach Bortle 1 to 2 on clear, moonless nights.
Best Dark Sky Parks in the USA
The United States has more IDA-certified International Dark Sky Places than any other country, with over 100 parks, sanctuaries, reserves, and communities recognized for their commitment to protecting dark skies.
The world's first International Dark Sky Park (2007), with pristine skies in remote southeastern Utah.
One of the best stargazing sites east of the Mississippi, with a dedicated dark sky viewing area.
Remote Chihuahuan Desert park with some of the darkest measured skies in North America.
Pristine skies above ancient bristlecone pines, with ranger-led astronomy programs.
Famous hoodoo formations under dark skies, home to an annual astronomy festival.
The lowest and driest point in North America, with wide-open desert skies.
Stargazing Near Me - How to Plan a Trip
You do not need expensive equipment or a long drive to enjoy the night sky. Use our dark sky map to find stargazing spots near you, then follow these tips.
- Check the moon phase -the darkest skies occur around a new moon. Even a half moon can wash out fainter stars and the Milky Way.
- Let your eyes adapt -it takes 20 to 30 minutes for your eyes to fully adjust to the dark. Avoid looking at your phone screen (or use a red filter).
- Check the weather -clear skies are essential. Cloud cover is the biggest obstacle to stargazing.
- Dress warmly -you will be standing still in the dark, often in exposed locations. Temperatures drop significantly at night, even in the desert.
- Start with binoculars -a pair of 10x50 binoculars will show you craters on the Moon, Jupiter's moons, star clusters, and more.
- Use a star chart app -apps like Stellarium or Sky Guide can help you identify constellations and planets in real time.
Dark Sky Place Categories
DarkSky International (formerly the International Dark-Sky Association) certifies dark sky locations in several categories, all of which are shown on our map.
- Dark Sky Parks -publicly or privately owned spaces with exceptional stargazing and quality outdoor lighting. Includes national parks, state parks, and other protected areas.
- Dark Sky Sanctuaries -the most remote and pristine dark sky locations, often far from any artificial light. These include Cosmic Campground in New Mexico and the Oregon Outback.
- Dark Sky Reserves -large areas with a dark core surrounded by communities that have adopted lighting policies to protect the night sky. The Central Idaho Dark Sky Reserve was the first in the US.
- Dark Sky Communities -cities and towns that have adopted quality outdoor lighting ordinances. Flagstaff, Arizona became the world's first dark sky community in 2001.
Frequently Asked Questions
Where are the best places to stargaze in the US?
The best stargazing is at IDA-certified dark sky parks, particularly in the western states. Utah alone has over 20 certified locations. Other top states include Arizona, New Mexico, Colorado, and Texas. Enter your ZIP code to find the nearest dark sky site.
How do I check light pollution in my area?
Enter your ZIP code or click your location on the map to see the nearest certified dark sky parks and sites, ranked by distance. Compare your area against the Bortle scale reference above to gauge roughly how dark your own sky is likely to be, then check the moon phase widget to see whether tonight is a good night to head out.
What is the Bortle scale?
The Bortle scale measures night sky brightness from 1 (darkest possible) to 9 (inner-city). Most US cities are Bortle 7-9. Suburbs are typically 5-6. You need Bortle 4 or darker to see the Milky Way. The darkest US locations in Nevada, Utah, and New Mexico can reach Bortle 1-2.
Can you see the Milky Way from the US?
Yes, but you need low light pollution -ideally Bortle 4 or darker. On a clear, moonless night at a certified dark sky park, the Milky Way is clearly visible. The best months are April to September when the galactic center is above the horizon. Use this tool to find suitable locations near you.
When is the best time to go stargazing?
The best conditions are on clear, moonless nights. New moon periods give the darkest skies -check our moon phase widget. The Milky Way core is best seen April to September. Major meteor showers like the Perseids (August) and Geminids (December) are spectacular from dark sky parks.
Do I need a telescope for stargazing?
No. The naked eye is all you need to see constellations, bright planets, meteor showers, the Milky Way, and occasional aurora. A pair of 10x50 binoculars reveals craters on the Moon, Jupiter's moons, the Andromeda galaxy, and many star clusters. A telescope adds more detail but is not necessary to enjoy the night sky.
Related Tools
- Sunrise & Sunset Calculator -Find sunrise, sunset, and golden hour times for any location
- Elevation Finder -Check the elevation of potential stargazing locations
- Measure Distance -Measure driving distances to dark sky sites
- Distance Between -Straight-line distance between two places