(Guidance: no audio on video clip.)
The object was spotted on Thursday, 23rd May, between 9 and 10pm, and puzzled the Ralston family so much that they filmed the activity from their Holywood home.
The light is seen moving erratically during dusk and as the sun goes down, the object becomes more obvious against the dark skies.
It is unclear what exactly the film shows and the UK's air traffic controllers, NATS, say they are not sure either.
The Ralstons wondered if it the light was a Chinese lantern, or kids playing, but then decided it was moving too quickly.
A spokesman told UTV there are no reports of the unusual activity matching that shown on the Ralston film.
And the mystery of the skies continues...