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

270
Shadow on Dec. 23
No Shadow in this direction on Dec 23
Immediately before 21st March
B C A On 21st March
Immediately after 21st March
No Shadow in this direction on 22nd June
W B C A E
JUNE when δ=φ
On 22nd JUNE
Fig. 48A Showing the locus of the extremity of the shadow on different
days at a latitude of 17°
Note. OA, OB are the shadows computed by Bhāskara when the Sun is on
the prime-vertical.
In the method of finding the shadow under verse 46,
we perceive Bhāskara's genius in (1) looking upon the
shadow as being made up of two segments namely that due
to φ and that due to the declination (2) in conceiving
what he calls Iṣṭa-drik-mandala palabhā, and Iṣṭa-drik-
mandala Krānti and (3) in deriving the equation
H sin D = (H sin ZT × H sin δ) / (H sin φ)
Latter half of verse 47 and verse 48. Something
to be noted.
In computing the shadow in a given direction, there
may be two shadows at times in the northern hemi-
sphere. When H sin a < Agrā and there will be none in
the southern. To compute the second shadow we have to
take 180 − L also as the latitude where L is the latitude
computed, and proceed in the same way as we have done
before.