The talented 31-year-old Harkness had perched himself in Dylan's Park, Dalkey - right on the coast - in order to pursue his photography habit after the extremely cold night offered up prefect conditions to shoot.
Graham told breakingnews.ie that he pointed his camera out over the Irish Sea towards Dalkey Island - at around 10.30pm last night - in order to get as many stars in his picture as possible, but little did he know the rarity of what he was about to catch.
The Terenure resident used a Canon 6d camera with a 14mm lens to take the shot below, utilising a 30 second long exposure technique.
"I was going for the stars over the island and I noticed something unusual after I looked at the picture," said Harkness.
Looking low at the left side of the horizon in the photo you can see a really bright object burning in the sky.
"It was way brighter than a normal shooting star - they are ten-a-penny when you're taking shots of the night sky."
"I knew this was different."
"I'm not astronomer, but I'm sure it was a meteor," said Graham.
Not being space experts ourselves we decided to contact Astronomy Ireland to get their thoughts.
"It is definitely a fireball or bright meteor," confirmed David Moore the editor of the Astronomy Ireland magazine.
"These objects come through the atmosphere at 70,000mph, burning up as they enter and are extremely rare to photograph."
Moore tells us that one of these objects may pass near Ireland about once a month, but that Astronomy Ireland are lucky to receive a single picture of one every year.
"We got one last year," added Moore. "But I couldn't tell you if we got one in the last couple of years before that. If we got ten of them in a decade, we'd be very lucky."
Have performed some calculations on the picture Moore, who plans to run the image in their next magazine issue, estimates that the fireball may have been overhead somewhere between England's Lake District and the Scottish Borders region.
Moore also believes that Harkness' picture shows the fireball right at its brightest because it is near the lowest point that these objects burn up - around 20kms above the ground.
"I really want to congratulate Graham, because the likelihood is that it will probably be the only time in his life he gets this kind of a photograph. Most professional astronomers will go through their whole career and not get one," noted Moore.
Moore has asked people to contact Astronomy Ireland here if anyone else saw the fireball at around 10.30pm last night. Any further sightings with help Astronomy Ireland in their efforts to effectively calculate the exact location of where the fireball was overhead.
Congratulations Graham! We'd imagine that picture is going right over the mantelpiece.