On March 6th and 7th, 2006, the near-Earth asteroid 2000 PN9 (also known as asteroid number 23187) will be flying by Earth, missing us by 2 million miles in the northern sky. The asteroid will be 12th magnitude those evenings as it races across the sky; users of 4- or 6-inch and larger telescopes should be able to see it creeping against the background stars — if they know exactly where to look. On March 8th it will be faded to magnitude 12½; on March 9th and 10th it will be magnitude 13.
To get an ephemeris (listing) of the asteroid's positions, for plotting on a highly detailed star atlas, use the JPL's HORIZONS system. The asteroid is so close that its apparent position will depend somewhat on your location on Earth, so in "Observer Location" enter a city near you. In "Time Span" choose a step value of 1 hour and enough steps to cover the nights you want. Then click "Generate Ephemeris." The times and dates in the output are in Universal Time. (To change this to Eastern Standard Time, subtract 5 hours.)