Portsmouth, NH Night Sky Brightness
How dark is the sky in Portsmouth, NH?
Portsmouth's sky measures suburban edge here. A noticeable glow near the horizon. Brighter stars and constellations are easy to pick out; the Milky Way is washed out. Portsmouth's sky is brighter than 28% of the 3,206 cities in this dataset.
Worth remembering: this is satellite radiance, not a ground observation. A true Bortle rating needs a human eye at night, this is the closest large-scale substitute, covered fully in the Bortle scale guide.
The nearest darker sky to Portsmouth
14 miles from Portsmouth, straight-line, sits Somersworth, NH, the nearest city here with a darker sky than Portsmouth's own suburban edge band.
Somersworth, NH is itself still a measured city, not a designated dark-sky park, this only compares against the 3,206 places this dataset covers.
Portsmouth against the rest of the dataset
Portsmouth, NH has a population of about 22,938, one of 3,206 US cities of 10,000 or more residents in this dataset. Ranked against the other 3,206 cities here by the methodology guide's own sampling, Portsmouth comes in at 894, darkest to brightest.