सिद्धान्तशिरोमणि: गणिताध्याय (भास्कराचार्य - ग्रहगणित, मध्यमाधिकार व स्पष्टाधिकार सटीक)

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elapsed tithis, integral or fractional (x + 12y)° will be the
longitude of the Moon. If, however, we consider y only as
the integral number of the elapsed tithis, we will have
obtained the Moon’s position from the formula (x + 12 y)°
at the ending moment of the tithi on the previous day.
The time in between this ending moment of the tithi and
the Sun-rise of the day concerned is known as Avama-
Sesha, since the Avama-days or Kshayāhas are the differ-
ence of days between the number of tithis in a given
period and the number of civil days during the same
period. In other words, the excess of a civil day over
a tithi which falls short of it, is the part of a civil day
that contributes towards the number of Kshayāhās in a
given period. Thus we have to compute the increase in
the Moon's longitude during the aforesaid Avama-Sesha
to obtain his longitude at the Sun-rise of the day concern-
ed. But this Avama-Sesha is of the form F { (t × K) / T }
where ‘ t ’ is the number of elapsed tithis upto the Sun-rise
of the day concerned K the number of Kshayāhas in a Kalpa,
T is the number of tithis in a Kalpa and F { (t × K) / T }
signifies the fractional part called Avama-Sesha, the integral
quotient having given the number of elapsed Kshayāhas.
Hence writing F { (t × K) / T } as R / T where R is the remainder
obtained by dividing (t × K) by T, the Avama-Sesha is of
the form R / T. This Avama-Sesha being mean solar. it has
to be rendered luni-Solar, which process is known as
चान्द्रीकरणम्. The rule of three used in this behalf is
‘ If for C civil days we have T tithis of the Kalpa, what
shall we have for R" / T ? The answer is (R / T) × (T / C) = R / C. This
then is the balance fractional part of a tithi that is there in
between the end of the elapsed tithi and the Sun-rise of the
day concerned. This part of a tithi is to be multiplied by
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