The extraordinary image was revealed to the audience at the Outer Limits Magazine 70 Years of the Modern UFO Era conference in Hull by UFO investigator Malcolm Robinson.
Mr Robinson, who has investigated UFOs since the 1980s, said it was the most remarkable UFO picture he has come across.
He told the audience that two men were photographing the BP oil refinery at Grangemouth, central Scotland, at night when they spotted a distant red object.
It then flew directly towards them, he said.
He said: “This red ball of light shot across towards them and was 200 to 300 feet above when he took the picture.eraoflight.com
“He literally had to bend over to take it.
“We checked with all the usual people and there was nothing in the area at the time.
“It is nice we got a photo. Is that evidence?
“I am here to tell you to open up your minds.”
Mr Robinson runs Strange Phenomena Investigations (SPI) based in central Scotland.
The image was sent to him in 1991 but remains one of the most compelling he has seen.
In an article on the SPI website, Mr Robinson said: “UFO testimony is one thing, but when you receive testimony backed up with a quite spectacular UFO photograph, well that’s another matter.
“We at SPI received quite an amazing UFO photograph which was unlike anything we have ever seen before.”
The incident happened on November 12 at around 9.30pm.
Phil Trevis, who snapped it was with a friend at the time.
In a report sent to SPI with the picture, he said: “My friend and I were taking photographs of the BP chemicals plant in Grangemouth (from Polmont Reservoir) when we noticed a dim, or rather, two small dim flashing lights over by the two ‘flashing pylons’ at Kincardine Bridge.
“We watched the object, which we thought was a helicopter, fly slowly over from the bridge to above the brightly lit Grangemouth Stadium.
“We watched it hover for around five minutes. It was then that we noticed that the ‘craft’ wasn’t making any noise.
“Normally, if it was a helicopter, we would have heard the blades. It then turned around and faced our direction.
“It was roughly 2,000 feet above the ground, then it dipped and increased dramatically in speed.
“At the point of the photograph, it was about 200 to 300 feet directly above us.
“It was then that we heard the light ‘pulsing hum’ of the object.
“My friend and I were quite shaken at the time, but afterwards had an overwhelming sense of excitement.”
“We ascertained that there was no aircraft activity in that part of central Scotland that night.
“Letters to the British Petroleum plant at Grangemouth, asking them if they had any small light aircraft or microlights in operation above their complex that night (on pipe inspection duty) came back stating that no such light aircraft or micro-lights were flying above the plant that night.”