What does "Bortle Scale" on the map mean? How should I interpret it?

Bortle scale from Class 1, the darkest, to Class 9, the brightest
© ESO/P. Horálek, M. Wallner - Representation of the Bortle scale
On this site, Bortle values are a quantitative interpretation derived from modeled SQM, not a traditional field classification. The original Bortle Scale is based on subjective visual observations. Expressing the result with decimal precision makes it easier to understand, compare locations, and choose observing sites. LightPollutionMap.app was the first website to display Bortle values in decimal form.

Is this website updated in real-time? How often is the data refreshed?

The latest completed annual satellite layer is 2025. The 2026 values are estimates and are revised as additional monthly inputs become available. The site is not a real-time light-pollution measurement service. For observing-site comparisons, read SQM together with the all-sky skyglow simulation rather than relying on a Bortle label alone.

What is "SQM" and how does it differ from the Bortle Scale?

SQM describes sky brightness on a continuous scale in mag/arcsec². On this site, the decimal Bortle value is a simplified quantitative interpretation derived from modeled SQM. It is intended to make comparisons and site selection more intuitive; it is not an on-site SQM measurement or a traditional subjective Bortle assessment.

How can I find the best stargazing locations near me?

United States light pollution map with dark sky and stargazing locations
US light pollution map with dark sky places and stargazing locations

Our system analyzes your approximate location based on your IP address and automatically displays the Bortle class for that area. You can also search for specific addresses or manually explore the map to discover optimal stargazing spots in other regions.

Can the map show aurora activity? Are there recommended regions for aurora viewing?

Aurora probability map with a color-coded northern lights forecast
Aurora probability map with the current northern lights forecast

Yes. Turn on the Aurora Probability layer to view the current NOAA-based aurora forecast. Treat it as a planning signal: local cloud, darkness, latitude, and forecast uncertainty still determine whether an aurora will be visible.

Can I use this to plan Milky Way photography sessions?

Yes. Use the light-pollution layer to shortlist darker locations, then open the all-sky skyglow view to compare directional brightness and the Milky Way at the selected sky time. Confirm moonlight, weather, access, and target timing before a shoot.

Is this map optimized for mobile use? Is there an app version?

This website is fully optimized for mobile devices, so it works smoothly anywhere. You can also check sky conditions and light pollution using the Free Stargazing APP.

Which countries or regions are supported? Is it a global map?

Global light pollution map with color-coded intensity by region
Global light pollution map showing worldwide distribution of artificial light at night
Yes, lightpollutionmap.app shows light pollution worldwide, covering most countries and regions. It's great for stargazers and travelers. We also offer a Chinese version at Darkmap.cn.

What's the source of the light pollution data? Is it reliable?

The 2025 annual layer is calculated independently by LightPollutionMap.app using NOAA VIIRS annual night-light data. Values labelled 2026 are provisional estimates, not a completed annual satellite layer, and are revised as additional monthly inputs become available. The map does not use DJ Lorenz's data or algorithms; only his color palette is used as a visual reference.

How can I share a specific location on the map?

You can go directly to a specific spot by adding coordinates to the URL: https://lightpollutionmap.app/?lat=25.3125&lng=-80.6875&zoom=8. Use this to share locations or bookmark your favorite stargazing places. Just change the latitude (lat), longitude (lng), and zoom level.

Is there a user community or feature for uploading observation reports?

We're planning to build a community for stargazing enthusiasts where users can upload field observation reports, photos, and suggestions. This will enrich our map data and allow users to share their observation experiences.

Is there a fee for using this service? What premium features are available?

Our website's basic features are permanently free to use. Currently, we don't have plans for a membership program, so you can use our light pollution map with confidence.

How can beginners get started with night sky observation? How does the map help?

The map helps stargazers quickly find suitable observation locations nearby and provides Bortle class information along with basic astronomical guidance. We plan to expand beginner tutorials and observation recommendations in the future to help you easily start your stargazing journey.

How can I reduce the impact of light pollution on astronomical observations?

To minimize the effects of light pollution on your astronomical observations, we recommend using Light Pollution Filters. These specialized filters can significantly improve visibility by blocking specific wavelengths of artificial light while allowing starlight to pass through. For quality options, check out Optolong Light Pollution Filters, which offer solutions for both visual observation and astrophotography.

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