Initializing, please wait a moment
How to Explore Bortle Scale Light Pollution 3D Explorer
Open the Bortle Scale Light Pollution 3D Explorer, drag the class slider from 1 to 9, and watch a 260-star sky field thin out exactly as the published scale describes.
- Open https://freetoolonline.com/space-3d/bortle-scale-light-pollution.html and wait for the star field and ground to render.
- Drag the Bortle class slider from 1 upward and watch faint stars vanish one by one as the limiting magnitude drops.
- Click "Excellent dark site (1)" then "City sky (8)" to see the full range in two clicks.
- Watch the Milky Way band fade and the horizon light dome rise as the class number climbs.
- Toggle "Milky Way band" or "Horizon light dome" off to see the star field alone.
- Read the facts panel for the current class's limiting magnitude, visible-star count, and Milky Way description.
Key published figures
| Figure | Value |
|---|---|
| Class 1 limiting magnitude | 7.6-8.0 |
| Class 5 limiting magnitude | 5.6-6.0 |
| Class 9 limiting magnitude | 4.0 or less |
| Published by | John Bortle, Sky & Telescope, Feb 2001 |
Next: the when guide or vs alternatives. Open the Bortle Scale Light Pollution 3D Explorer.
Why trust these tools
- Ten-plus years of web tooling. The freetoolonline editorial team has shipped browser-based utilities since 2015. The goal has never changed: get you to a working output fast, without an install.
- No install, no sign-up. Open a tool and get a working output in seconds - nothing to download and no account to create. Tools that need heavy processing run it on our service, so even a low-powered machine gets the job done.
- Analytics stops at the page view. We measure which pages get visited, not what you type or upload inside a tool. There is nothing to sign in to and no profile is attached to your input.
- Open-source core components. The processing engines underneath (libheif, libde265, pdf-lib, terser, clean-css, ffmpeg.wasm, and others) are public and audit-able. We link to each one in its tool page's footer.
- Free, with or without ads. All tools are fully functional without sign-up. The Disable Ads button in the header is always available if you need a distraction-free run.