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

328
OG = Gnomon ; OP = Shadow of the gnomon ;
PM = the Bhuja drawn from the extremity of the shadow
P perpendicular on the East-west line ; OM = Koti of the
shadow extending along the East-west line. AB is the
Nalaka placed along the Chayakarṇa PG. The eye is
placed at A and the planet ☉ is visible through the tube
of the Nalaka AB.
Fig. 62
Verses 105, 106 and 107. The method of observing
through the instrument called Nalaka, the planetary
position.
On a horizontal plane mark a point and through it
draw the East-west line and also the North-south ; if the
planet is in the East mark off the computed Koti of the
shadow towards on the East-west line; if the planet is in
the Western hemisphere, mark this Koṭi towards the East.
From the extremity of the Koti mark the computed Bhuja
perpendicular to the East-west line and draw the computed
shadow from the point so as to form a right-angled