YozoraAtlas

How dark is the sky in Northern Ireland?

Sky darkness for 14 towns and parks in Northern Ireland, worked out from NASA satellite images of light at night (2025). 8 of them have skies of Bortle 4 or darker, where the Milky Way shows overhead. The darkest is Islay (21.77, Bortle 3), the brightest Belfast (17.95, 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 Northern Ireland with every place marked

Darkest skies in Northern Ireland

  1. IslayBortle 321.77
  2. the SperrinsBortle 421.34
  3. the Causeway CoastBortle 421.28
  4. the Antrim Coast and GlensBortle 421.26
  5. BinevenaghBortle 421.13

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 Northern Ireland

  1. BelfastBortle 817.95
  2. DerryBortle 718.80
  3. BangorBortle 619.04
  4. LisburnBortle 619.05
  5. CraigavonBortle 619.09

All 14 places in Northern Ireland

Amber names are parks and certified dark-sky places. The figure is the Bortle class: 1 darkest, 9 city center.
Bangor6Belfast8Binevenagh4Craigavon6Derry7Islay3Lisburn6Strangford Lough4the Antrim Coast and Glens4the Causeway Coast4the Lagan Valley6the Mourne Mountains4the Ring of Gullion4the Sperrins4