A fine night and a great procession of planets brought about 50 people to Whanganui's Ward Observatory on July 13.

They were able to see Jupiter with its moons, Saturn with rings and moons, and Mars, which just looks like an orange blob and is as close to Earth as it ever gets.

It was a fortunate time, observatory secretary Mark Lee said, with the annual procession of planets making the five usually visible from Earth all visible at on the same night.

"At 6.45 Venus would be the brightest planet over to the west, then Mercury, Jupiter would be about overhead and Saturn, with Mars across to the east."

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The observatory is open on fine Friday nights and usually manned by Lee and Wanganui Astronomical Society president Ross Skilton.

In the days leading up to July 13 they expected good viewing and posted on their Facebook page that the observatory would be open.

Lee spent the evening inside, looking at Saturn through the Cooke telescope. It is said to be the largest unmodified refractor in use in New Zealand and is especially good for looking at planets.

"It's got a very long focal length, so you get whatever colour is visible. On Friday Saturn was only just yellow, or beige - not quite white."

People could see its rings, the gaps between the rings, and two of its moons. Jupiter is enormous and has four moons that change position night by night. All of them were visible that night, through a smaller telescope set up outside at the observatory.

The International Space Station has also been visible at times in the past few weeks. It is manned by six people and Lee logs his location in the free Heavens-Above website to find out when it will be visible.

"It rotates the Earth at 17,500km/h, and gets around in 93 to 94 minutes. It can only be seen when the sun is on it because it is not lit up," he said.

Viewing could be even better this coming Friday, if the sky is clear. The observatory in St Hill St opens at 7.30pm and stays open as long as people are interested.

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Jupiter should be visible near a quarter moon, and lighting should make the moon's crevasses and features visible.