"The comet makes its closest approach to Earth (0.41 AU) on Feb. 24, 2009. Current estimates peg the maximum brightness at 4th or 5th magnitude, which means dark country skies would be required to see it. No one can say for sure, however, because this appears to be Lulin's first visit to the inner solar system and its first exposure to intense sunlight.
Surprises are possible. "
Full artical please go to:

http://science.nasa.gov/headlines/y2009/04feb_greencomet.htm