Tune is not a town as such......it is a parish in Østfold county, with church records going back to 1720. It included the town of Sarpsborg (originally Borg), which was established as a separate parish in 1859. Other parts of the original parish have also been separated from Tune, for example Kråkerøy (1686), Varteig (1860) and Rolvsøy (1910). Tunøya is a small island in the river Glomma, and I believe it belonged to the Tune parish. On a 'secular' level, Tune is today a part of Sarpsborg kommune since 1992.
Hi Stef - I do have been researching Tune, since my grandfather Vilhelm Hansen was born there in 1902. He was Methodist and his birth and baptism were registered in Sarpsborg. There are some aerial pictures of the area on a website. Would you like me to send you the link? What is your last name - perhaps we are related?