SYDNEY (Reuters) - Radio hams and amateur astronomers around the world spent the weekend bouncing radio conversations off the Moon to one another in commemoration of the Apollo 11 landings 40 years ago, organizers in Australia said Sunday.

Although they had some clear and extensive conversations, they had to be patient. It takes around 2.5 seconds for a radio signal to reach the Moon and bounce back to another part of the Earth, so it took around five seconds to get a reply.

Initiated a few months ago by science buffs in Australia and the United States, 'Moonbounce' was just winding up on Sunday Australian time after a 24-hour special event that organizers hope will become annual.

It brought together hundreds of amateur radio hams around the world, event co-founder Robert Brand told Reuters, some armed with their own radio dishes.

It was timed to coincide with the 40th anniversary next month of the Apollo 11 landings on July 20, 1969. But as the Moon does not orbit directly around the Earth's equator, this was the nearest weekend organizers could arrange for practical reasons.

Among those taking part was Apollo 8 astronaut Bill Anders, one of the first men to orbit around the Moon, who took a famous photograph of Earth from space now known as "Earthrise."

While most were amateurs, institutions lent equipment to the event, including a 26-meter dish at Mount Pleasant in Tasmania and a 45-meter dish at Stanford University in the United States.

"The signals go up from these dishes in a tight beam to the Moon. They actually hit the ground and at an atomic level 'shake' all the atoms on the surface of the Moon," said Brand.

"It is still taking place as we speak."

Around 1,000 people around the world are thought to have the kind of equipment to do this kind of messaging and Brand, who as a 17-year-old played a minor role in the Apollo missions by helping install telecommunications installations used by NASA in Australia, said the results were remarkably clear.

There was "very little difference quality-wise" to some common radios, he said.