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

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triangle with the Bhuja and Koti. Extend a thread from
the point of intersection of the bhuja and shadow to meet
the gnomon's top so as to form the Chāyākarṇa or the
hypotenuse of the right-angled triangle of which the other
sides are the gnomon and the shadow. Along this thread
place the Nalaka such that the lower extremity of the
Nalaka coincides with the eye. Seeing through the Nalaka,
the planet is to be seen. I shall tell how the planet could
be seen in water as well.
Comm. The Nalaka is a simple tube formed generally
of bamboo. The purpose of this is to verify the correct-
ness of the computation of the shadow and its bhuja. If
the computation is wrong the planet will not be seen in
that direction. It might be asked how the shadow and
bhuja are pertinent with respect to a planet, whose shadow
cannot be observed as that of the Sun. True, but the
computation of the shadow and bhuja are done as will be
done with respect to the Sun, knowing the declination etc.
as in the case of the Sun. Computation does not depend
on the observation of the actual shadow. Computing the
magnitudes of the Bhuja and Koti, the direction of the
Chāyākarṇa points to the planet in the sky.
Verse 108. Observing the planet through the Nalaka
in water.
Fig. 63
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