Star gazers got their telescopes and binoculars ready over the weekend, trying to spot an asteroid which came closer to the Earth than any space rock of its size has in 77 years.

The 800-metre-wide asteroid whizzed over North American skies late Saturday, missing the planet by about 530,000 kilometres, slightly farther away than the Moon but still a "near miss" by astronomers' standards.

Several amateur astronomers in Edmonton almost missed their chance to see the asteroid, known as 2002-NY40. Rain and cloud cover made for poor visibility.

Edmonton star gazer

But then shortly after midnight, they detected the asteroid hurtling through the constellation Hercules beside the star Vega.

"It's over right beside a fairly bright star," one person announced.

Star gazer David Roles said it was a moment he'll never forget. "Oh I'm really happy that we got a glimpse of it," he said. "Because it's not very often we see an object that close to the Earth."

Sara Poirier of the Ontario Science Centre in Toronto said it was easiest to spot the asteroid under the darkest of night skies.

To put the asteriod's size into perspective, scientists described it as being roughly eight times the size of a regulation Canadian football field.

But looking at it from Earth through a telecope, it appeared to be nothing more than a shooting star.

Professor Peter Brown of the University of Western Ontario said while the asteroid posed no danger to Earth, it was important to track its speed and rotation.

"If the day ever comes that we ever need to go out and divert one of these things and determine how we can move it then we need to understand its physical properties," he said.

In June, an asteroid the size of a soccer field missed the Earth by 120,000 kilometres, less than one-third the distance to the moon.

Now, that the 2002-NY40 asteroid has come and gone, scientists are shifting their focus to another rock heading towards Earth, which is more than two kilometres wide. Its approach is expected in 2019.