About the Bortle Scale Estimator
Estimates your sky's Bortle class from visual cues, an SQM reading, or direct lookup.
What it is
Three ways to find your Bortle class: a guided questionnaire about what's visible in your sky, a direct Sky Quality Meter (SQM) reading mapped to the standard correspondence table, or browsing the full reference table of all 9 classes.
Features
Guided questionnaire
Plain-language questions map to a best-estimate class.
Reference table
All 9 classes with name, limiting magnitude, and description.
SQM input
Maps a magnitude-per-arcsecond reading to the nearest class.
Honest framing
Explicitly noted as approximate, not a precise measurement.