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

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THE TRIPRAŚNĀDHIKĀRA
Verse 1. The purport of this chapter.
Pandits say that this is the science of time in as
much as, herein there is described the method of knowing
the direction and the point of space (where a celestial body
is situated) given the time. Hence I expound that
chapter, which gives that knowledge and which abounds in
very important statements, which forms the quintessence
of the science of astronomy.
Comm. This chapter is called Tripraśnādhikāra,
since this deals with the three questions pertaining to the
direction and the point of space of a celestial body for
a given time ie. dealing with Deśa, Dik and Kāla. In
this chapter we come across the Hindu methods of
spherical trigonometry, and gnomonics or Śaṅkuvedha
or observations with the help of a gnomon. Also we find
herein a usage of what is called ‘Golayantra’ or the
armillary sphere, which helped the Hindu astronomers to
solve all diurnal problems. We find herein Bhāskara
excelling himself. This chapter abounds in a good number
of technical terms and without a knowledge of this
chapter, no one could call himself a Hindu astronomer.
Verses 2-4. To compute what is called lagna given
the time.
The lagna or the ascendant as it is called or the point
of intersection of the ecliptic with the horizon at a given
point of time is obtained as follows. Obtain the Sāyana
longitude of the Sun at the point of time at which it is
required to find the lagna. Supposing the Sun is in the
rth degree of a particular Rāśi, the number of asus which