From today, 23 October through to Sunday 25, amateur astronomers worldwide plan to celebrate the 400th anniversary of Galileo's telescope and his celestial discoveries.

Distant Suns from First Light for iPhone and iPod touch promises a way to join them.

Distant Suns uses the compass on the new iPhone 3GS to identify the planets, constellations, over a hundred galaxies and star clusters, and thousands of stars.

"Distant Suns gives users a faithful reproduction of the sky now or in the future or even back in Galileo's time," explains Distant Suns inventor Mike Smithwick.

"On Galilean Nights you'll see just how far we've come since Galileo first aimed his handmade telescope toward the heavens 400 years ago. An event which quite literally changed the world."

"Learning about the night sky is much easier now than in Galileo's time. It is hoped that seeing Jupiter's four largest moons - called 'Galilean Moons' - will increase interest in what the night sky has to offer."

Available from the Apple iTunes App Store, Distant Suns costs £2.39 and requires the iPhone 2.2.1 Software Update or later.

Distant Suns has a long history, having been first published for the Commodore Amiga in 1987.