Location and sky settings
Search a place, enter coordinates, then choose or estimate local sky conditions.
Dark-sky finder from compared sites
Generated sky report
Location Comparison
Compare multiple observing sites from darkest to brightest.
| Site | Coordinates | Distance | Bortle | SQM | Darkness | Stargazing | Astrophotography | |
|---|---|---|---|---|---|---|---|---|
| No comparison sites added yet. | ||||||||
Understanding Light Pollution and Dark Skies
What is light pollution?
Light pollution is unwanted artificial light that brightens the night sky and reduces visible stars. Streetlights, buildings, advertising, stadiums, and poorly shielded outdoor fixtures can scatter light into the atmosphere. The effect is strongest near cities, but skyglow can travel far beyond urban boundaries. Astronomers often describe these conditions using the Bortle scale, which ranges from Class 1 for exceptional dark skies to Class 9 for heavily illuminated inner-city skies.
How this map generator helps
This tool converts selected Bortle and sky-brightness values into an easy planning report. Users can mark coordinates, compare observing sites, adjust moon illumination, cloud cover, transparency, and elevation, then review estimated astronomy suitability. A colored map overlay helps visualize relative local intensity around the selected point. The overlay is intentionally illustrative, so it should not be treated as calibrated satellite data.
Choosing a better observing site
Dark-sky planning usually involves more than finding the lowest Bortle number. Moon phase, clouds, haze, elevation, local lighting, and horizon obstructions can significantly affect visibility. A Bortle 3 site with poor transparency may produce weaker results than a Bortle 4 site under crisp, dry air. Astrophotographers should also consider travel safety, power availability, wind, and legal access before selecting remote locations.
Reading your results
The generated darkness score estimates how favorable the selected conditions are for deep-sky viewing. Stargazing and astrophotography ratings combine the chosen sky class with moonlight and cloud penalties. For reliable field work, compare this report with a dedicated weather forecast and current astronomical conditions. Save the result as CSV for data analysis or PDF for a portable field reference.
Practical observing tips
Arrive before darkness, avoid direct white light, and allow your eyes time to adapt. Shield nearby lights when possible and use dim red lighting for equipment. Even small reductions in local glare can improve contrast. Revisit the same site on different nights because atmospheric transparency can change dramatically. Combining dark skies with low moon illumination usually gives the strongest Milky Way and deep-sky views.
Bortle Scale Reference
| Class | Environment | Typical SQM | General Sky Quality |
|---|---|---|---|
| B1 | Excellent dark sky | 21.76–22.00 | Exceptional |
| B2 | Typical dark site | 21.60–21.75 | Excellent |
| B3 | Rural sky | 21.30–21.59 | Very Good |
| B4 | Rural/suburban | 20.80–21.29 | Good |
| B5 | Suburban | 20.00–20.79 | Moderate |
| B6 | Bright suburban | 19.10–19.99 | Poor |
| B7 | Suburban/urban | 18.00–19.09 | Very Poor |
| B8 | City | 17.00–17.99 | Severe |
| B9 | Inner city | < 17.00 | Extreme |