If in referrring to Kinbote as the Great Beaver, Nabokov was
indeed indicating a reference to the constellation Gemini, then the
pail, "situla," turns out to indicate the constellation Aquarius.
Situla is a star in the constellation Aquarius, but the name also is an
alternate name, along with Ganymede, for the constellation and refers to
the source from which Aquarius/Ganymede pours out the water/wine. It seems that
in most cultures this constellation is associated with rains, floods,
fountains.
One interesting astrological interpretation reads "The beauty
of Ganymedes and his flight through the air link [Situla] to the ideas of
personal charm and aviation with which [the constellation] is certainly
connected." The beauty of Ganymede has other Pale Fire implications, and
reflects on "Hebe's Cup."
Ursa Major has some Pale Fire
links: 1) as indicating northernmost; 2) the mythical Atalanta was
suckled by a she-bear; 2) the seven stars of the constellation are
associated in some cultures with death, and may have something to do with the
seven regalia-bearing courtiers that appear at the time of Queen Blenda's
death 4) The Bear is associated with the chase (another Atalanta
link).
Other constellations spotted in Pale Fire: Lyra, Krater,
Cygnus, Virgo, Felis, Canis, Cancer, Monoceros.