Trondsen family - Australia

I have never joined a forum before, so hope you will treat me kindly. I am the great granddaughter of Harald Trondsen who, according to his marriage certificate (Sydney, Ausralia), was born in Norway and married Agnes Andersen, also born in Norway, in Sydney in 1880. Harald's father, as shown on the marriage certificate, was Halvor or Halbor Trondsen or Tronsen. He was Norwegian and the certificate states he was a policeman and was married to Maria Dunn. There is a story in our family that Harald was a mariner who jumped ship in Sydney, New South Wales, Australia. Also, that some of our forebears travelled from Norway to the USA and settled in Utah. Then some migrated to Australia, via New Zealand. Rose Trondsen. Harald's sister, left the ship in New Zealand and married a man whose surname was Andersen. He was a ships chandler. Our name was changed from Trondsen to Thompson in Australia, presumably because the names sounded similar and my ancestors did not know how to read or write to correct the spelling. There are no Trondsens left in Australia. Hoping someone can help me to try and track down any information. Thanking you in advance.