YozoraAtlas

How dark is the sky in Guarda?

Sky darkness for 2 towns and parks in Guarda, worked out from NASA satellite images of light at night (2025). 1 of them has skies of Bortle 4 or darker, where the Milky Way shows overhead. The darkest is Serra da Estrela Natural Park (20.88, Bortle 4), the brightest Guarda (19.93, Bortle 5). Milky Way season in Guarda runs March to August: on moonless nights the bright core stands clear of the horizon, climbing to about 21° 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 Guarda with every place marked

Darkest skies in Guarda

  1. Serra da Estrela Natural ParkBortle 420.88

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

Brightest city skies in Guarda

  1. GuardaBortle 519.93

All 2 places in Guarda

Amber names are parks and certified dark-sky places. The figure is the Bortle class: 1 darkest, 9 city center.
Guarda5Serra da Estrela Natural Park4