How dark is the sky in Castelo Branco?
Sky darkness for Castelo Branco (18.93, Bortle 7), so far the only place in Castelo Branco on Yozora Atlas, worked out from NASA satellite images of light at night (2025). Milky Way season in Castelo Branco runs March to September: 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
Darkest skies in Castelo Branco
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 1 place in Castelo Branco
Amber names are parks and certified dark-sky places. The figure is the Bortle class: 1 darkest, 9 city center.