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

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vertically with the help of a plumb-line. Draw a circle on
the horizontal plane having the foot of the gnomon as the
centre and any arbitrary radius. Draw the East-West and
North - South diameters of the circle. The longitudes of
the Sun when the shadow of the gnomon lies along the
East - West diameter give the gola Sandhis. Note the
direction of the shadow daily after the day when his
shadow is along the East - West line. If the Sun rises
thereafter a little towards North of the East point, then he
is said to be in the uttara gola; his shadow will be a little
south of the East - West line. The point at which the
Sun thus begins to rise north of the east point, is the Meṣa
gola Sandhi or the vernal equinox. Gradually the Sun
goes on rising at points which are farther and farther away
from the East point. When he has reached the extreme
north point, ie when the gnomon's shadow is extreme
south, he is at the Cancer. Similarly when he rises at the
extreme South point on the horizon, he is at Capricorn.
Bhāskara actually noted these four points and the longi-
tudes cited above were given by him as the Gola Sandhis
and Ayana Sandhis. Indirectly, he could know that
the Ayanāṁśas at the time of his writing the book,
were 11°.
Verses 3 to 6. Speciality with respect to the
Moon.
Let the Hsine and Hcosine of the tropical longitude of
the pāta (Rāhu the ascending node of the lunar orbit) as
per the smaller table of Hsines when the radius is taken to
be 120', be respectively multiplied by 123 and 7 and
divided respectively by 4 and 12. The results are known
as the Bāhuphala and Koṭiphala respectively. According
as the tropical longitude of Rāhu ie λ be such that as
270° < λ < 90° or 90° < λ < 270°, the Bāhuphala is to be
divided by 362 ± Kotiphala. Subtract the result from
the Gola Sandhis and Ayana Sandhis of the Sun, to get
those of the Moon.