Having just looked through recently reported magnitudes for C/2006 P1
appearing on the ICQ website and elsewhere, I think a word of caution
is in order. The range in reported magnitudes is becoming
extraordinarily large and some infer very dramatic day-to-day
increases taking place over the last couple of days.

Under normal circumstances, one would not expect the comet's apparent
magnitude at this time to be increasing by more than a few tenths of
a magnitude per day and, in fact, it should be just about leveling
off with perihelion only two days away. Likewise, any forward-
scattering effects should probably not yet have become very apparent,
so I have to wonder if perhaps some observers are not simply getting
a bit carried away. Admittedly, I haven't seen the comet myself since
Monday but based on very long experience in observing comets, I find
it difficult to accept some of what I'm seeing reported.

Since C/2006 P1 offers the almost unique opportunity to document a
possible forward-scattering event, observers need to make every
effort to report m1 values of the greatest possible accuracy, even
given the difficult circumstances under which the comet must be
observed. Simply going by "impression" or by adjusting magnitude for
extinction factors amounting to 4 and 5 magnitudes, make such
brightness estimates of little scientific value.

JBortle