Conjunction A Once In A Lifetime Viewing Opportunity

Some interesting viewing coming up over the next few days in the skies to the southwest.

The planets Jupiter and Saturn are lining up in such a way, they're going to be very bright in the sky around dusk.

Astronomer James Durbano, from the Big Sky Astronomical Society says even though the planets are far apart, they're going to look very big and very close together to us here on Earth.

"Jupiter is about 778-million kilometres away, Saturn is about twice as far away, about 1.4-billion kilometres away. But from here on Earth they're going to appear almost at exactly the same spot in the sky. They're going to look like they're perfectly lined up."

Durbano says it should be a spectacular sight.

"They're going to be so close together, that if you have your telescope pointed in that direction and you're using an eye piece that provides a low magnification, you should be able to fit both of them into the view at the same time. Which is very rare to be able to fit two planets into the field of view through a telescope at the same time."

Durbano says the best viewing is around sunset.

"You don't have very much time to see them. Each and every evening shortly after sunset you've only got perhaps about an hour or so to see them. Because, if you wait too long what'll happen is they too will set. So the Sun will set first and then an hour or so later these two planets will set. And of course once they set, you can't see them."

He says the two planets align about every 20 years, but not in an orbital plane with the Earth so we can't see it.

He says the last time the two planets lined up so close with Earth was about 400 years ago but it was difficult to see because they were so close to the setting Sun.

But he says 800 years ago, during the middle ages, they were as close together as they'll be by Monday, December 21.