The famously private Neil Armstrong, the first man to walk on the moon, has been coaxed into giving a rare interview -- with an Australian accountant.

The 82-year-old has long been reluctant to discuss the 1969 mission that enthralled the world, and has granted only a handful of interviews since.

But the Certified Practicing Accountants of Australia convinced him to film an hour-long one-on-one in which he talks about the landing and his famous first steps on the moon.

"A month before the launch of Apollo 11, we decided we were confident enough we could try and attempt... a descent to the surface," said Armstrong in the video which appeared on the CPA website this week after the interview last year.

"I thought we had a 90 percent chance of getting back safely to Earth on that flight but only a 50-50 chance of making a landing on that first attempt."

CPA head Alex Malley said he suggested the idea to the space veteran when he was in Australia last year helping the organisation with its 125th anniversary, and he agreed.

"I know something not a lot of people know about Neil Armstrong -- his dad was an auditor," Malley told News Limited newspapers.

"The most compelling thing I felt about him was his humility -- his commitment to his team, his deference to everyone except himself, his respect for the Russians -- I found that quite extraordinary."