Cut and pasted from here....
http://ltvt.wikispaces.com/Kaguya+Impact
If the impact accidentally occured on an earlier orbit, the geometry might be as shown in the preceding images. For example, an impact at 14:30 UT could be observed in a relatively dark sky from Hawaii.
It should perhaps also be noted that LTVT assumes the impact will occur at a normal "sea level" point on the Moon's dark surface. If Kaguya hits an area that is higher or lower than that, the flash point will be displaced by a small amount radially.
Foing suggests that due to uncertainties in the flight path and surface topography, the impact may actually occur during the spacecraft's closest approach to the Moon on an earlier orbit, 2 or possibly 4 hours prior to the expected time. In that event, it might possibly be visible from Hawaii (although in daylight unless 4 hours early).
