The rural area has a 70km/h speed limit and no street lighting.
Mr Yun was dressed in black apart from a light blue cap and light coloured sneakers, the finding said.
Central Otago crash analyst Senior Constable Alastair Crosland told the inquest into Mr Yun's death that the area was lightly populated, with few pedestrians during the day.
Senior Constable Chris Blackford said the area would have been pitch black at the time and he suspected Mr Yun had "moved out into the roadway to get a better look at the stars" through a gap in the tree canopy.
As Mr Yun did so, a 4WD Ford Ranger vehicle was driving along the same road with its headlights on low-beam, the finding said.
"Mr Yun, who was facing the vehicle, failed to step off the road and the driver of the vehicle failed to see him until it was too late to avoid a collision.
"Mr Yun was struck by the extreme front left corner of the Ford Ranger and was thrown to the side of the road."
The driver of the vehicle stopped his car and discovered Mr Yun on the side of the road. He then contacted emergency services and began CPR.
St John Ambulance arrived but Mr Yun could not be revived, the finding said.
Coroner McElrea found Mr Yun had inadvertently placed himself in a dangerous situation and failed to react to oncoming danger.
"The evidence would indicate he was distracted at the time, probably stargazing, but had he been wearing light coloured or high visibility clothing it is likely he would have been seen in time for the collision to be avoided."
The driver was not found to have been at fault.
