With our interpretation it follows that62 synodic months =1,830 days, i.e., 1 synodic month ª29.515 days.Since this value is not very accurate (the modern value is 29.530589 days), the
ancient Indian ritualists should have put an adjustment rather frequently –
addition of one day is necessary about every 64 months – in order to keep the
relation of the date of rituals and the lunar phases. But there are many textual
evidences which show the use of this five-year yuga, for instance, the Arthas ́a ̄stra
as mentioned above, the medical text Sus ́rutasam.hita ̄, the Buddhist text
S ́a ̄rdu ̄lakarn.a ̄vada ̄na, and the Jain text Su ̄ ryapannatti. It was only after the intro-
duction of Hellenistic astronomy that the calendrical values were improved to a
useful degree.
2 Naks.atraand Lunar Astrology
2.1 Two systems ofnaks.atra
Sometime in the later Vedic period the meaning of the word naks.atrashifted from
its original sense of “star” in general to its narrower sense, namely, one of the
28 or 27 groups of stars which were regarded as the lunar stations along the
ecliptic. The earliest list ofnaks.atrasin this sense is found in the Taittirı ̄yasam.hita ̄
(Macdonell and Keith 1912: 409–31). The names of the naks.atrasshow some
variations and their grammatical forms do not always agree. In table 18.1 the
most commonly used forms are given. When 28 naks.atrasare counted, Abhijit
is put between Uttara ̄s.a ̄d.ha ̄ and S ́ravan.a. The most important difference between
the 28 naks.atra system and the 27 naks.atrasystem is that in the latter each
naks.atraoccupies an equal space of 13°20¢while in the former the distance is
irregular. When, therefore, we find a naks.atraname in Sanskrit texts, we should
know which of the two system is intended. Since similar systems of unevenly
spaced 28 lunar mansions are found in Chinese and Islamic astronomy, there
have been disputes concerning their origin. In my view, the Chinese and Indian
systems are independent while the Islamic mana ̄zil al-qamar(stations of the
moon) should have been influenced by the Indian naks.atras.
The identification of stars comprising each naks.atraposes even more difficult
problems, but some secure identification can be made: for example, Kr.ttika ̄is a
group of stars corresponding to Pleiades, and Citra ̄ is aVirginis (=Spica).
In the earlier Sanskrit texts naks.atras are counted from Kr.ttika ̄, while in the
later period As ́vinı ̄ (bandgArietis) became the first mansion. The shift of
the starting point of the naks.atrasystem can be ascribed to the precession of
the equinoxes. The time when Pleiades was near the vernal equinox is about
378 michio yano