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

64
to take the elapsed tithis from the previous Chaitra and
the Suddhi of the previous year. Also in this case the
Dhruvakas pertain to the commencement of the previous
Solar year.
Comm. Easy.
Verse 15. To obtain the position of the Sun.
The number of the days in the Ahargaṇa is to be
diminished by 1/60 part of itself to obtain the number of
degrees, and fractions thereof; then the Ahargaṇa multi-
plied by three and divided by 22 gives the minutes and
fractions thereof. Adding the two results we get the
position of the Sun.
Comm. The mean daily motion of the Sun is
0-59-8-10-21. Here 59' = 1° - 1' = (1 - 1/60)°; for x
days x (1 - 1/60)° = x° - x°/60 as mentioned. The remain-
ing part namely 0-0-8-10-21 = 9807'/72000; Converting this
into a continued fraction it is equal to 1/(7 +) 1/(2 +) 1/(1 +) 1/(12 +) ...
of which a good convergent is 3'/22. Hence for x days 3x/22
as stated in the verse.
Verse 16. To obtain the position of the Moon.
The number of elapsed integral tithis multiplied by
12 and added to the Sun's position in degrees, gives the
Moon's position in degrees at the ending moment of the
tithi preceeding the day at the Sun-rise of which the
planetary positions are sought. To find the position at
the Sun-rise required, ten times the Kshaya-dina-Sesha
increased by 1/7 th of itself gives the number of minutes to
be added to the position got above.