Night Sky Brightness · Sicily and southern Italy
One number for how dark your night still is
Project NSB is a small group of amateur astronomers. Since 2024 we have been measuring the brightness of the night sky over Sicilian and southern Italian towns with pocket photometers, and publishing what we find in plain tables.
- Kalsa, Palermo17.64
- Monreale18.92
- Cefalù19.63
- Polizzi Generosa20.71
- Piano Battaglia21.58
From the Palermo seafront to the Madonie: 2025 medians in mag/arcsec². A higher number means a darker sky.
A volunteer, a meter, a moonless night
Light pollution is easy to complain about and hard to pin down. A street looks bright or it doesn’t. The sky seems worse than it was when you were young. Neither statement can be checked.
So on clear nights around each new moon, our volunteers go to fixed points in their own towns, hold a pocket photometer straight up and write down what it says. The result is one figure, in magnitudes per square arcsecond. Repeat it at the same spot, by the same rules, for long enough, and you can compare one district with another, one season with the next and one year with the last.
Read the full method. It fits on a laminated card.
Why measure it at all
Three reasons we give when someone asks what we are doing on their roof.
The sky is a shared landscape
From the Kalsa you can pick out a few dozen stars on a good night. Two hours’ drive away, at Piano Battaglia, you cannot begin to count them. Nobody voted on that difference.
You cannot judge a change without a “before”
Street lighting across the south is being refitted, town by town. Whether a new scheme helps or hurts can only be shown against earlier readings, and those exist only if someone took them.
Night is habitat
Moths, migrating birds and the loggerhead hatchlings on Ionian beaches all depend on darkness. Light that goes upward lights nothing for us, and it costs energy to send it there.
- 17.6Kalsa, Palermo
- 19.6Cefalù
- 21.6Piano Battaglia
The same circle of sky at three of our readings, simulated. Only the sky glow changes.
The project in three figures
- 28
- fixed measuring points in 11 towns and cities, from Trapani to Matera
- 3,060
- readings logged since March 2024, across 612 measuring sessions
- 38×
- how much brighter the sky overhead is in Palermo’s Kalsa than at Piano Battaglia in the Madonie
Counts to 30 September 2026. The comparison uses 2025 medians.
A year of one number
Both skies brighten in summer, when haze and Saharan dust scatter more light back down. The Kalsa swings by 0.51 over the year. Piano Battaglia swings by 0.22, because up there the air has far less light to scatter.
Show these figures as a table
| Month | Kalsa | Piano Battaglia |
|---|---|---|
| Jan | 17.82 | 21.66 |
| Feb | 17.79 | 21.63 |
| Mar | 17.71 | 21.60 |
| Apr | 17.66 | 21.59 |
| May | 17.58 | 21.56 |
| Jun | 17.46 | 21.52 |
| Jul | 17.35 | 21.47 |
| Aug | 17.31 | 21.44 |
| Sep | 17.49 | 21.53 |
| Oct | 17.62 | 21.57 |
| Nov | 17.74 | 21.62 |
| Dec | 17.68 | 21.64 |
Latest updates
Summer season 2026: haze, dust and one clear result
196 sessions at 28 points. Dust cost us some darkness in June, Palermo held steady, and the change at Ragusa Ibla is now hard to dismiss.
Perseids week: 41 sessions in six nights
The August new moon landed on the Perseid peak. It gave us our busiest week so far, and a small lesson from the beach at Mondello.
Your first session: a note for new volunteers
What to bring, what to do when you get there, and the five mistakes nearly everyone makes the first time.
We are short of people, not equipment
You don’t need a telescope or any background in astronomy. You need two or three free evenings around each new moon, a street or rooftop you can get to, and the patience to stand still for twenty minutes. We lend you a meter and come along on your first session.
Right now we most need people in Siracusa, Reggio Calabria and Cosenza.