RE: Brightness

KIRK3KHAN (KIRK3KHAN@aol.com)
Tue, 13 Jan 1998 05:43:49 EST

I would like to express apreciation for Rob Matsons explanation of brightness.

I'd just like to comment on a  phenomonen that all may not be famaliar with.
Below is from a friend, Zdenek Kopal, and his book, "The Realm of the
Terrestrial Planets"

"Did you ever stop to note the illumination of a moonlit landscape at
different phases of the moon?  If you had measured it you would have found
that, although the moon occupies only twice as large an area in the sky as it
does at its first or last quarter, the night of the full moon is not twice,
but 15 to 17 times as bright as that of the first quarter  was a week before,
or the last quarter will be a week later.  In particular, within a few hours
of the full moon (and remember that not all full moons are equally full) a
surge in intensity of lunar illumination is truly conspicuous, a fact which
could not be true if oblique sunrays were illumination a smooth surface, no
matter what it substance might be.  It can be understood only if the small
scale structure of the lunar surface is highly vesicular (honeycombed) and
capable of very strong backscattering.  In other words, the moon acts like a
mirror."


Dan Poeder