Bright Asteroid Visible Tonight
Ender, Duke_of_URL writes: "NASA is reporting that 1998 WT24, a near Earth asteroid, will be easily visible (9th magnitude) to telescopes in Auriga and Perseus. This NEO will be passing within 5 lunar distances to Earth, so there's no danger of collision."
The distance for a collision is by definition Earth's radius, which is 0.0166 lunar distances. The "twenty lunar distances" rule you're talking about is for long term probabilities of a collision over many many orbits.