Iceland / Ireland in 15 days and looking for suggestions

I am planning a trip to Iceland and Ireland for 15 days in late October. I am flexible with where and how long to spend in each location. I will be traveling solo- if that makes a difference. My initial thought was to spend 5 days in Iceland and another 10 days in Ireland but can adjust if necessary. I would like to see the northern lights and the beautiful landscape of Iceland- as much variance as possible, and for Ireland I haven't a clue...Castles, pubs, giants causeway and the cliffs of moher stand out. I am open to suggestions. I will be renting a car if that helps. Am I packing too much into too small of a window of time? I don't want to stretch myself too thin but am willing to sacrifice some sights to make it more enjoyable. Any suggested itineraries or attractions would be greatly appreciated.... :)