For 19-year-old Jamie Crawford it was a dream come true when he was able to reach for his camcorder and record his sighting.
An expert has confirmed the images are genuine.
"I've always wanted to see a UFO and to catch one on tape is a real bonus," said Mr Crawford of Marjoram Walk, Banbury. "I was very excited and shaking like mad while I filmed.
"We were just serving food in our back garden and I saw something peculiar out the corner of my eye. I got the camcorder and a soon as I zoomed in I thought 'I've caught a UFO'."
Mr Crawford said to the naked eye the object was about the size of a thumb nail and glinted in the sun. It was visible for about seven minutes and seemed to float slowly upwards at an angle before disappearing.
From his Hanwell Fields home the object was southeast, the same direction of the now disused RAF Upper Heyford airbase. The incident took place at about 7pm on Thursday June 8.
Mr Crawford said: "One of my friends was a bit sarcastic at first when I pointed it out in the sky, but then he admitted it was a bit weird.
"I've always believed in aliens and this has confirmed my theories. I'm not sure what they'd be doing here, maybe monitoring how we live, but I'm going to keep checking the skies."
Mr Crawford's video footage was converted to stills by a technician at Oxford and Cherwell Valley College's Banbury campus media department.
Kevin Robinson, programme manager for media and performing arts, witnessed the transfer and said the images on the camera looked genuine and reflected real structure, not digital distortion or ghosting.
Suggestions in the editing suite included a Harrier jump-jet, Chinook helicopter and squashed fly, though Mr Robinson's personal preference was a Stealth bomber.
"At that distance and zoom if it was heading towards the camera before banking and heading away it might give the false impression that it was hardly moving," he said.
"It seems an awful long way for aliens to come just to watch someone's barbeque, but whatever it was it was definitely there."