At 6:25pm AEST, the ISS, which looks like a fairly bright, moving star, will appear low in the north-western horizon. It will rise and pass very closely to both Jupiter and then Venus.

The space station circles the Earth regularly but seeing these these three objects in the sky at once, particularly with the two planets so close together was unusal Mount Stromlo Observatory's Roger Franzen said.

"This is a rare event," he said. "The fact that Venus and Jupiter are conjuct at the moment is unusual. Whilst it is a regular event its on a timeline of hundreds of years."

He said from our perspective on earth Jupiter was passing behind Venus. The two planets have have been the brightest objects other than the moon in the night sky for more than a month.

Mr Franzen supplied a visualisation of what Canberran is in store for.

"The green line represents the plane of the ecliptic, in other words the plane that planets orbit the sun in," he said.

"The top right quadrant or the north west near the constellation Leo you have the fat blue dot which is Venus and the not so fat yellow do which is Jupiter."

Finding a position with a clear view of the horizon was advised to watch the rare astronomical event.

"Get a compass and set it for west north west," he said.

"Look for the horizon and find a spot where you can see it clearly. You will see the ISS rising. It will be unmistakable as it will be a bright and fast moving star."

For the digtially savvy star-gazers the technical manager of the Advance Instrumentation and Tehcnology Centre recommended downloading an ISS tracker app for your smartphone.