The Bortle scale is a nine-step description of how dark a sky looks. Class 1 is a pristine wilderness sky; class 9 is the glowing core of a large city. You do not need an instrument to estimate your class. Look up and count what you can see.
Quick field test
In a class 1 to 3 sky the Milky Way casts structure and shadow, and the zodiacal light is obvious. Class 4 to 5 skies still show the Milky Way overhead but lose it near the horizon. In class 6 to 7 you see the Milky Way only as a faint smear, often after letting your eyes adapt. Class 8 to 9 skies show a handful of stars and a bright gray-orange dome; the Milky Way is invisible.
Why the Moon and clouds matter more some nights
Light pollution sets a floor, but weather decides the night. A clear class 6 suburb can beat a hazy class 4 field. Conversely, a bright Moon can wash out a genuinely dark site. Use the forecast's cloud and Moon details before blaming your location.
Cheap improvements that work
Shield direct light: turn off porch lights, close blinds facing your observing spot, and stand so a building blocks the nearest streetlamp. Give your eyes 20 to 30 minutes without looking at a phone. Travel 20 to 30 minutes away from town if you can; the drop in skyglow is often larger than the drive suggests. A hood or a dark cloth over your head helps more than most filters.
Filters are not magic
Broadband light-pollution filters cannot restore a washed-out sky. Narrowband filters help a few nebulae under moderate glow, and a Moon filter simply dims a bright target. Save the money for fuel to a darker site.
Be a good neighbor
Use warm, shielded fixtures aimed down. Light that escapes sideways wastes electricity and ruins the view for everyone within a mile. You do not need a dark-sky ordinance to make your own yard meaningfully darker tonight.
Sources and review
Updated October 21, 2026. Date-sensitive details can change.