How dark is the sky in Zemgale?
Sky darkness for 5 towns and parks in Zemgale, worked out from NASA satellite images of light at night (2025). 3 of them have skies of Bortle 4 or darker, where the Milky Way shows overhead. The darkest is Sauka Nature Park (21.76, Bortle 3), the brightest Jelgava (19.11, Bortle 6). The bright core of the Milky Way never climbs clear of the horizon haze anywhere in Zemgale while the sky is fully dark; the rest of the band passes overhead, with the longest moonless nights from September to March.
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 Zemgale
Among the places on this site. Plenty of land between them is just as dark, with no town or park to name it by.