YozoraAtlas

How dark is the sky in Vysočina Region?

Sky darkness for 4 towns and parks in Vysočina Region, 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 Žďár nad Sázavou (20.13, Bortle 5), the brightest Jihlava (19.51, Bortle 5). The bright core of the Milky Way never climbs clear of the horizon haze anywhere in Vysočina Region while the sky is fully dark; the rest of the band passes overhead, with the longest moonless nights from September to April.

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 Vysočina Region with every place marked

Darkest skies in Vysočina Region

  1. Žďár nad SázavouBortle 520.13
  2. Havlíčkův BrodBortle 520.04
  3. TřebíčBortle 519.88

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 Vysočina Region

  1. JihlavaBortle 519.51

All 4 places in Vysočina Region

Amber names are parks and certified dark-sky places. The figure is the Bortle class: 1 darkest, 9 city center.
Havlíčkův Brod5Jihlava5Třebíč5Žďár nad Sázavou5