YozoraAtlas

How dark is the sky in Leinster?

Sky darkness for 17 towns and parks in Leinster, 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 the Slieve Bloom Mountains (21.32, Bortle 4), the brightest Dublin (17.63, 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

NASA satellite night-lights map of Leinster with every place marked

Darkest skies in Leinster

  1. the Slieve Bloom MountainsBortle 421.32
  2. the Wicklow MountainsBortle 420.88
  3. the Cooley PeninsulaBortle 420.71

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 Leinster

  1. DublinBortle 817.63
  2. CelbridgeBortle 718.90
  3. DroghedaBortle 619.06
  4. NewbridgeBortle 619.15
  5. KilkennyBortle 619.22

All 17 places in Leinster

Amber names are parks and certified dark-sky places. The figure is the Bortle class: 1 darkest, 9 city center.
Athlone6Bray6Carlow6Celbridge7Drogheda6Dublin8Dundalk6Kilkenny6Mullingar6Naas6Navan6Newbridge6Portlaoise6Wexford5the Cooley Peninsula4the Slieve Bloom Mountains4the Wicklow Mountains4