YozoraAtlas

How dark is the sky in Lisbon?

Sky darkness for 3 towns and parks in Lisbon, worked out from NASA satellite images of light at night (2025). None of them have skies of Bortle 4 or darker, where the Milky Way shows overhead. The darkest is Azambuja (20.06, Bortle 5), the brightest Lisbon (17.92, Bortle 8). Milky Way season in Lisbon runs March to September: on moonless nights the bright core stands clear of the horizon, climbing to about 22° at its highest.

19 Bortle class, 1 pristine to 9 city center park or dark-sky place city

Numbers like 21.95 or 16.97 are the brightness of the sky overhead on a clear, moonless night, in mag/arcsec². The scale runs backwards: a lower number means a brighter sky, from about 22 for a natural sky to about 17 in a city center.
How the readings are made

NASA satellite night-lights map of Lisbon with every place marked

Darkest skies in Lisbon

  1. AzambujaBortle 520.06
  2. Torres VedrasBortle 519.62
  3. LisbonBortle 817.92

Among the places on this site. Plenty of land between them is just as dark, with no town or park to name it by.

All 3 places in Lisbon

Amber names are parks and certified dark-sky places. The figure is the Bortle class: 1 darkest, 9 city center.
Azambuja5Lisbon8Torres Vedras5