AS part of his day job, Michael Davidson measures radioactivity levels around nuclear power stations on behalf of the Government.

His wife Christine is a chemistry lecturer at the University of Strathclyde.

They were joined in Glasgow this weekend by history professors, train drivers, lawyers, health industry insiders and biologists for a major science-fiction convention on the banks of the Clyde.

Satellite 4, the 65th British Science Fiction Convention, is the UK's largest annual gathering of its kind. The event, which has taken over the Crowne Plaza Hotel, is expected to net the city in the region of £1.6 million.

Running until tomorrow, it covers literature, film, art, music and space science and was brought to Glasgow by a committee of volunteers who have been preparing since winning a bid to host the event more than two years ago.

Programme organiser Christine and convention chair Michael says the event had sought to combine science fact and fiction, incorporating literature and art with talks from renowned scientists, including astrophysicist Dame Jocelyn Bell Burnell, who discovered radio pulsars but is also a fan of "space poetry".

And even the world of science fiction has not escaped the debate on Scotland's constitutional future, with time set aside for a discussion on what will happen to the event, also known as Eastercon and held across Britain, if Scotland votes for independence.

"It's about science fiction and science fact combined, and how one permeates the other," Christine says. "Some scientists read sci-fi as children and it leads to them becoming scientists. Some science fiction is becoming science fact. We've got authors and artists but also very famous scientists."

The event is expected to attract up to 900 delegates over the weekend. According to John Wilson, who caught the convention bug in 2000 and has since travelled across the world to attend events, it is impossible to define a typical science-fiction convention-goer.

"We get everything from a train driver to a nuclear physicist," he says. "It's basically a short holiday - it's fun and it's a way to relax. A lot of science-fiction fans have fairly high-powered jobs with a fair amount of pressure, and they need a break.

"You do get a high proportion of geeks. If you throw a hat in the air you can guarantee it will hit a computer specialist on the way down. Social skills can be a little bit lower on the priority list, and would be regarded as sub-par on the outside.

"A tribe is probably a good way to describe it, but it's a very varied tribe. I think it's an accepting atmosphere - people don't judge you. You can't judge a book by its cover, and that's true here. You will find some of the warmest, most caring people around."

Delegates from America, Russia and Scandinavia were expected to travel to Scotland for this weekend's convention. They filled the Crowne Plaza, leaving organisers to make use of overflow rooms in nearby hotels. Eastercon follows the success of the massive WorldCon, which brought thousands of international sci-fi fans to Glasgow in 2005.

Guillermo Vildosola and wife Patricia are visiting Scotland for the first time. The couple moved to Nottingham from the US last year after he accepted a transfer from firm Reckitt Benckiser, where he works in pharmaceuticals.

"The conventions are a little smaller here but the people might be a little more wonderful," says Patricia, who is dressed in the Victorian-inspired sci-fi style known as "steampunk". She adds: "I've always liked playing dress-up and my mother is a Star Trek fan so there's never been a time when there wasn't science fiction in my life."

Edward James, a retired professor of medieval history, travelled from London. Now aged 66, he attended his first sci-fi convention in 1964. "The appeal is in meeting friends and talking to them and other like-minded people," he says. "There's a lot of people who like the same sort of books I like - and that's it really.

"The conventions have got bigger. There were about 200 at the first one I went to, now 1000 is a standard number, but we talk about the same stuff.

"There's a lot of interesting things happening but you can also just stand about and drink rather nice pints of real ale."