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

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the ecliptic, parallax appears to decrease the latitude so
that we have to decrease the Sapātasūrya.
The proportion that 70' of latitude correspond to 15°
of Sapāta-chandra is due to the formula
H sin 15° ✕ H sin 4½
—————————— = H sin β. Using logarithms,
R
log sin β = 9·4130 + 8·8946 = 8·3076 so that
β = 1° - 10' = 70'. This proportion could be used
because the Moon is within 15° of the Node. Hence when
we are investigating the occurence of a solar eclipse,
application of rule of three is not unjustified or crude.
Herein, Bhāskara assumed the zenith-distance of
the nonagesimal to be round about 45° and drew a
conclusion that the effect in the longitude on account of
parallax in latitude is one-sixth of the zenith-distance.
Instead if the zenith-distance be assumed to be z, the
result would be (48' - 43" ✕ sin z ✕ 15) / 70 = 21/2 sin z which
may be taken as a better approximation. If, on the other
hand the modern value of 57' of the lunar parallax be
taken, the result would be (57 sin z ✕ 15) / 70 = 12 sin z
approximately which is a better value.
In this calculation, it is better to compute the zenith-
distance of the nonagesinal using modern methods instead
of assuming the nonagesimal to be on the meridian.
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