All the zodiacal constellations are thus included in the
nakshatras except Capricorn, for which Aquila and Delphinis are
substituted. These, as well as Hydra, are a considerable distance
from the ecliptic, but may perhaps be nearer the moon's path, which,
as already seen, slightly diverges from it. But this point has not
been ascertained by me. The moon completes the circuit of the heavens
in its orbit round the earth in a little less than a lunar month or
27 days 8 hours. As twenty-seven nakshatras were demarcated, it seems
clear that a nakshatra was meant to represent the distance travelled
by the moon in a day. Subsequently a twenty-eighth small nakshatra
was formed called Abhijit, out of Uttarashadha and Sravana, and this
may have been meant to represent the fractional part of the day. The
days of the lunar month have each, as a matter of fact, a nakshatra
allotted to them, which is recorded in all Hindu almanacs, and enters
largely into the Joshi's astrological calculations. It may have been
the case that prior to the naming of the days of the week, the days of
the lunar month were distinguished by the names of their nakshatras,
but this could only have been among the learned. For though there
was a nakshatra for every day of the moon's path round the ecliptic,
the same days in successive months could not have the same nakshatras
on account of what is called the synodical revolution of the moon. The
light of the moon comes from the sun, and we see only that part of it
which is illuminated by the sun. When the moon is between the earth
and the sun, the light hemisphere is invisible to us, and there is
no moon. When the moon is on the opposite side of the earth to the
sun we see the whole of the illuminated hemisphere, and it is full
moon. Thus in the time between one new moon and the next, the moon
must proceed from its position between the earth and the sun to the
same position again, and to do this it has to go somewhat more than
once round the ecliptic, as is shown by the following figure. [215]