When space agency NASA wants to check on threats in space from asteroids or comets, one of the people they call on is a 66-year-old Chingford man, working on his home computer.

Former karate teacher and construction worker, Dr Steve Guest qualified as an astrophysicist in 2013 after taking a five-year online course in the subject to gain his doctorate. Hanging on the wall of his home are certificates from NASA in recognition of his painstaking, but important service to the wellbeing of mankind.

Steve told the Guardian that the work, as part of the minor planets, asteroid and comet group, involves comparing photographs of space, in a meticulous grid layout, to what the skies looked like in previous years. That way any unusual objects or changes can be spotted and reported back to Berkeley University in California, USA.

He says: “I am one of many people around the world working on this. If I see a change, I report it to Berkeley, then they inform NASA and space telescopes are moved to see what is happening. We need to know within a year of likely impact to be able to do anything about it.”

Any asteroids that are the size of a double decker bus could be a danger to earth, says Steve. “But it is the speed that really counts. Imagine the devastation if something hit Earth at 75,000 mph,” he adds.

An astrophysicist is also an astronomer and Steve says he does take a close look at the skies on clear nights. He unfortunately had to give up work in 2010 when he was diagnosed with a severe lung complaint and could not work.

“I have always been fascinated by space,” he says. “I don’t believe in little green men, but I do think there is a civilisation out there like ours. We could meet up in about 1,000 years’ time. If I was the one to spot anything important in space I would name it after my dog Niki. It would be called something like B27 Niki.”

But Steve hopes he will never spot anything so dangerous to our world.