How dark is the sky in Slovakia?
Sky darkness for 57 towns and parks in Slovakia, worked out from NASA satellite images of light at night (2025). 22 of them have skies of Bortle 4 or darker, where the Milky Way shows overhead. The darkest is the Poloniny Dark Sky Park (21.70, Bortle 3), the brightest Bratislava (18.33, Bortle 8).
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 Slovakia
- the Poloniny Dark Sky ParkPrešov Region · Bortle 321.70
- East Carpathians Protected Landscape AreaPrešov Region · Bortle 421.61
- Muránska planina National ParkBanská Bystrica Region · Bortle 421.53
- Slovak Karst National ParkKošice Region · Bortle 421.48
- Slovak Paradise National ParkPrešov Region · Bortle 421.42
Among the places on this site. Plenty of land between them is just as dark, with no town or park to name it by.
Darkest place in each region of Slovakia
| Region | Places | Dark places Bortle 1 to 4 | Darkest place |
|---|---|---|---|
| Banská Bystrica Region | 9 places | 5 dark | Muránska planina National Park21.53 · Bortle 4 |
| Bratislava Region | 4 places | 1 dark | Záhorie Protected Landscape Area20.74 · Bortle 4 |
| Košice Region | 6 places | 2 dark | Slovak Karst National Park21.48 · Bortle 4 |
| Nitra Region | 6 places | 0 dark | Šaľa20.00 · Bortle 5 |
| Prešov Region | 10 places | 5 dark | the Poloniny Dark Sky Park21.70 · Bortle 3 |
| Trenčín Region | 8 places | 3 dark | Ponitrie Protected Landscape Area21.26 · Bortle 4 |
| Trnava Region | 4 places | 1 dark | Dunajské luhy Protected Landscape Area20.79 · Bortle 4 |
| Žilina Region | 10 places | 5 dark | the Veľká Fatra Dark Sky Park21.32 · Bortle 4 |