During Nikki's concert, he says:
[Nikki]
Lo! The stars doth
twinkle in accord
with our song...
The brighter one is the
Star of Diarmuid...
And next to it the Star
of Grania can be seen
shining so faintly...
We mariners navigate
our vessels by these
two stars!
Now, I don't know of any real stars with those names, but
Diarmuid comes from Irish mythology. Meanwhile, Grania, at first, doesn't seem to relate to anything, but I quickly realized it should actually be Gráinne from the same tale (which is pronounced like "grania", I believe).
Are these the only named celestial bodies in the Chronoverse? I'm wondering if these two stars belong to the "five brother stars" told by Belthasar to represent the Dragons. Curiously, during the same concert, Nikki drops the line "Neptunian nymph", which suggests the presence of a Neptune in Chrono history as well, either as a mythological figure or a planet. Or it could just be a grammatical quirk.