The thin 175 mm diameter disk weighing 344 grams was analysed by a team from the University of Warwick who traveled to Muscat in November 2016 to collect laser scans of a selection of the most important artefacts recovered from the wreck site.
Astrolabes are considered to be the rarest and most prized of artefacts to be found on ancient shipwrecks, with only 104 known examples in the world.
Prof Mark Williams said: “Using 3D scanning technology has enabled us to confirm the identity of the earliest known astrolabe, from this historians and scientists can determine more about history and how ships navigated.
“Using technology normally applied within engineering projects to help shed insight into such a valuable artefact was a real privilege.”
The artifacts were discovered by David Mearns of Blue Water Recoveries, the oceanographer who in 2001 located the wreck of the Second World War Royal Navy battleship HMS Hood, and Bismark, the German ship which sunk it.
“Without the laser scanning work performed by WMG [Warwick] we would never have known that the scale marks, which were invisible to the naked eye, existed,” he said.
“Their analysis proved beyond doubt that the disk was a mariner’s astrolabe.
“This has allowed us to confidently place the Sodré astrolabe in its correct chronological position and propose it to be an important transitional instrument.”
Until these new discoveries, the oldest official ship’s bell was dated 1509 and carried aboard the Mary Rose, which sunk in the Solent in 1545, meanwhile The oldest known astrolabe was from from another Portuguese shipwreck, tentatively identified as the Bom Jesus that sank in 1533 off the coast of Namibia.
They are described in a study published in The International Journal of Nautical Archaeology.