Starting tonight, skywatchers will be treated to a rare convergence of the five planets visible from earth with the naked eye. Mercury, Venus, Mars, Jupiter and Saturn will continue to cluster closer together until mid-May, when they will quickly disperse. The next chance to see them so tightly grouped won't happen for another 38 years. Bob Bonadurer is director of the Minneapolis Planetarium. He says the planets will look like a string of pearls in the sky: