There are 13 programmes a year - to tie in with the lunar calendar - and Moore has never missed one. The early editions were transmitted live from the BBC's Lime Grove Studios and had to carry on regardless, even when Moore once inadvertently swallowed a fly during a broadcast. Though it is hardly big-budget - it rarely strays beyond Moore in a studio interviewing a guest - The Sky at Night still nets more than one million viewers ("if it precedes the snooker, it can get four or five million," according to the programme's producer, Pieter Morpurgo). Many directors of observatories have attested to the fact that they were first turned on to astronomy by The Sky at Night.
But what accounts for the extraordinary longevity of the programme? Moore himself puts it down to the endless fascination of the subject. "It's all around us," he asserts. "You can't help seeing the sky and the stars and wanting to know more about them."
For his part, Morpurgo reckons the programme appeals because "There's so much mystery to astronomy. One of Patrick's phrases when he has been interviewing an astronomer is, `It's all very interesting, but we really don't know yet'. In discovering so many things, something like the Hubble telescope is only raising a lot more questions. It's the ongoing uncertainty. We don't yet know where the edge of the universe is - why not? Because they're building better and better telescopes all the time. We don't even understand how the sun works - and that's only 93 million miles away. If a subject is all wrapped up, then interest in it wanes because there's nothing further to add. Astronomy is a subject that's never-ending."
Moore got the stars bug when at the age of six he read GF Chambers' Story of the Solar System. Having subsequently written more than 50 books on astronomy, he is currently revising his Atlas of the Universe. Even at the age of 74, Moore is still enth-using that "There's so much to learn. An astronomer said to me: `I thought I knew everything about the constitution of the stars in 1925. Then I knew less in 1930 and even less in 1935.' The more you know, you realise the less you know. Astronomy teaches us how insignificant we are. We ought to be rather more sensible."
In Morpurgo's view, Moore's boundless zest for his subject is another reason for the enduring popularity of The Sky at Night. The astronomer was up until 2.30am on the morning of our interview "tracking Martian duststorms". "He's an eccentric enthusiast," observes the producer. "Whenever he talks about astronomy, he's bubbling over with enthusiasm - as though it's the first time he's ever talked about it. We had an afternoon off in America recently and went to Disneyland where people kept stopping him. Even the guys on passport control at Heathrow ask for his autograph. His warmth generates interest in him, as well as in the subject. People write in to say, `I don't know what he's talking about, but I love Patrick Moore'."
Moore gets 30 to 40 letters a day from fans, all of which he replies to personally. Only a few are from loonies. "One wrote to me," he recalls, "and said: `I enjoyed your programme and wanted to buy an army tank. Have you got any?'"
A cricket nut who still gets hatfuls of wickets with his medium-paced leg breaks, Moore is content with life. Only two species get him down: politicians and astrologers. "What a mob they are in the House of Commons," he snorts. "There's only one man we need in Parliament - Guy Fawkes.
"And I have no time for astrology whatsoever," he says. "With the millennium approaching, every crackpot is coming out of the woodwork. Astrology proves one scientific fact: there's one born every minute."
`Eyes on the Universe', the 40th-anniversary edition of `The Sky at Night', is on tomorrow at 11.40pm on BBC1Reuse content