Away from Callanish it's all about alignments. Where will the moon rise/set at it extremes when viewed from various monuments? It's a similar thing to the year alignment at Newgrange, but it only happens once every 18.6 years.
I think know a site where the moon will rise out of Howth, which I might check out. I'll try my best to keep the results for the book :-)
I think Dowth is another one to check out ...
Ooh the possibilities!