Halvor Halversen

I am a kiwi researching my family history. I am trying to find out anything I can about my great great great grandfather, Albert Halverson. This is his anglisised name that he took when he came to New Zealand. He was born circa 1856. His birth name is Halvor Halversen Torpse - except the 's' has a diagonal stroke like 'Ø', could this possibly be an outdated Norwegian letter...? I have conflicting info about his place of birth: Bergen and Valders are cited. I have scanned copies of postcards from Valders, and I believe this is most likely where he was born / lived. I thought perhaps he moved to Bergen, and / or left Norway from Bergen. I'm having trouble finding his name anywhere. I also have the ship's name, which seems to be no help. It was apparently called the 'Aratura'. This sounds like an odd name for a ship in those days, and it also sounds like it could be of Maori origin, and therefore would have been a New Zealand ship. It arrived, probably in Auckland, in 1879. I am also thinking that if it was a kiwi ship, it probably did not travel very far and may have been a connection from a ship landing in Australia. I am yet to find any record of him emigrating either. Though I have narrowed it down to just Bergen, so if this Bergen info is completely wrong I guess I am barking up the wrong tree. it could possibly have been Oslo, as it is the closest major city to Valders (not to be confused with Valdres[:)]). Any help is much appreciated!