article: The line-up includes Mercury, Venus, Saturn, Mars and Jupiter and is best viewed from southern parts of the northern hemisphere. In Northern Ireland, astronomers say all five planets should come into view simultaneously by about 24 January. The Irish Astronomical Association said it will be a "sight not to be missed". However, successful planet spotting will depend on local weather conditions and the amount of cloud in the sky. Terry Moseley, a former president of the Irish Astronomical Association, said Mercury, Venus, Saturn, Mars and Jupiter are the only five planets that are ever visible from Earth with the naked eye, but it is rare to see all of them at once. He said that in the UK, the alignment would be visible in southern parts of England first and should come into view in Northern Ireland a few days later, as it lies further north. Mr Moseley added that four of the planets can be seen from Northern Ireland at the moment on clear nights, but added that "elusive little Mercury" is always the hardest to see because it is closest to the horizon. "Mercury will be easiest to see from about 28 January to 2 February, but you should start looking from about 24 January in case the skies are cloudy later," Mr Moseley advised skywatchers. "You should start looking from about 45 minutes before sunrise, and you'll need a good clear horizon to the south east," he added. "Venus will be by far the brightest, a brilliant beacon above the south east horizon. Look about a hand-span to the left of Venus, and slightly below it, to try to spot Mercury, which will be much fainter, and not easy to find in the twilight glow." The director of Armagh Observatory, Mark Bailey, said the last time such a view was visible was January 2005. He will be talking to schoolchildren in Tandragee library, County Armagh, on Thursday, explaining what to look out for. Skywatchers will have to distinguish the row of planets from some very bright stars. Mr Bailey said that one of the brightest stars in the sky - Arcturus - will also form part of the alignment view, along with another star, Spica, more or less vertically below it. Observatory staff have produced images showing the alignment on the morning of Friday 22, January, shortly before Mercury is expected to come into view. Mr Moseley added: "The group will be joined by the waning crescent moon from 1 February onwards, making an even more glorious sight." The pre-dawn sky show is best viewed from high ground, in places were there is little light pollution. "You need a good, dark view towards the southern horizon," Mr Bailey said. He suggested locations such as Divis mountain in Belfast; the Sperrins in counties Londonderry and Tyrone and Slieve Beagh near the border with County Monaghan. The alignment will be visible from some areas until 20 February, but both local astronomers advised that the window will be much shorter in Northern Ireland as Mercury will disappear from view several days earlier.
summary: Skywatchers are about to get a rare chance to see five planets align in the night sky in a celestial show that has not been seen for more than a decade.