I have seen down to mag 7 on some exceptional nights with an atmosphere measured at 1.5 to 1.6 arc secs on those occasions. Most average clear nights are about mag 6. The location is remote and in fact according to Phillips Dark Sky atlas it is one of those black areas on the map. The cloud conditions are 30 percent better than the coastal area, where you would expect orographic uplift of warm currents coming from the coast. The observatory is located on the Sligo/Roscommon border.
I stayed in Cahirdaniel in Kerry earlier this year (Derrynane hotel....about 50 metres from the sea). The skies were spectacular. The best i have ever seen in fact. I was on Velencia Is during the day. I'd say the Island is great for dark skies.
Paul C
My next scope is going to be a Vixen VMC200L Catadioptric OTA
  