The summer season ran from 1 March to 30 September, with 196 sessions at 28 points. That brings the project total to 612 sessions and 3,060 readings since March 2024.
| Point | 2025 | 2026 | Change |
|---|---|---|---|
| Politeama, Palermo | 17.14 | 17.11 | −0.03 |
| Kalsa, Palermo | 17.49 | 17.43 | −0.06 |
| Catania centre | 17.38 | 17.36 | −0.02 |
| Cefalù seafront | 19.58 | 19.55 | −0.03 |
| Ragusa Ibla | 19.06 | 18.87 | −0.19 |
| Erice (TP-02) | – | 20.04 | new |
| Piano Battaglia | 21.53 | 21.51 | −0.02 |
A negative change means the sky got brighter. Changes smaller than 0.1 are within our margin of error.
Dust
Three episodes of Saharan dust reached the region, in late April, mid-June and the first week of July, and we flagged 23 sessions. Dust scatters whatever light is already in the air, so its effect depends on how much light there is. On the worst night, 17 June, the Kalsa read 17.09, which is 0.34 below its seasonal median. Piano Battaglia read 21.37, only 0.14 below.
Palermo
The Kalsa is down 0.06 on last summer. That is inside our margin of error, so we are not reporting it as a change. Ask us again in a few years.
Ragusa Ibla
Last winter Ibla was down 0.15. This summer it is down 0.19, about 19% brighter than a year ago. That makes two seasons in a row above our threshold, while the other Ragusa point, RG-01, has not moved. We now treat this as a real change. The likely cause is still the white floodlighting added along the valley road in 2025.
Erice’s first season
TP-02 gave us nine usable sessions from 17 attempts, close to the one-in-two we expected, with a median of 20.04. The cloud is winning, but only narrowly.
What’s next
The winter season began on 1 October. The autumn meter comparison at Piano Battaglia is planned for the new moon of 9 November.