“How dark is your sky?” Estimating artificial light in Ireland from satellite imagery, 2015-2019

Local Election Areas (LEAs) are groupings of Electoral Divisions. Note that certain of the 166 LEAs have been combined together resulting in a total of 130 LEAs for analysis.

When interpreting LEAs, it is important to note that areas named for urban areas such as Ballincollig- Carrigaline can also include significant rural or undeveloped areas with very low light emissions. 

All ten LEAs with highest light emissions  in January 2019 are located in Dublin. The highest is Pembroke South Dock (69.94) followed by North Inner City (59.15), Crumlin-Kimmage (38.81), Rathgar-Rathmines (31.86) and Tallaght Central (26.71). Outside of Dublin, the highest LEA was Galway City East (13.04). 

South and West Kerry had the lowest light emissions in January 2019 (0.42) followed by West Mayo (0.45). These low readings are of particular note since the areas contain the respective "Deep Sky Reserves" of Ballinskelligs and Ballycroy National Park, where active measures are taken to reduce artificial light - so low emissions levels would be expected here. Other areas with very low light emissions include Conamara, Galway (0.46), Ballinamore, Leitrim (0.47), West Cork (0.48), West Clare (0.49), Manorhamilton, Leitrim (0.49), Glenties, Donegal (0.49) and Killaloe, Clare (0.50)

In general, the areas with lowest light intensity are found along the Western seaboard, as well as other areas inland generally associated with more mountainous areas. The large urban areas also stand out more clearly as “light islands” from the surrounding countryside.