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

402
Latter half of verse 33. To know the magnitude of
the eclipse at any given moment during the course of the
eclipse.
Let the product of the time elapsed from the moment
of first contact and the length of the path of the eclipsing
body traced from the moment of the first contact to the
middle of the eclipse divided by the time between the
moment of first contact and the middle of the eclipse, be
x. Similarly let the product of the time before the end of
last contact and the path of the eclipsing body traced
between the middle moment of the eclipse and the moment
of last contact divided by the time between the middle
moment and the moment of last contact be y. Lay off
x and y units of length from the first and last points of
the path of the eclipsing body along the path respectively.
Then we get the points of the centre of the eclipsing body
at the required moments. With these points as centre
and radius p, if circles be drawn, they represent the
eclipsing body. The length of the diameter of the eclipsed
body shaded, gives the magnitude of the eclipse called
grāsa.
Comm. Here rule of three is applied namely “If
during time T₁ or T₂ a path equal to l₁ or l₂ in length is
traced what length will be traced in times t₁ or t₂?”,
where T₁ and T₂ are the times called Sparsa-Sthiti-Khanda
and Mokṣa-Sthiti-Khanda respectively, l₁ and l₂ are the
times elapsed from the moment of first contact or before
the moment of last contact and t₁, t₂ are the times from
the beginning of the eclipse and before the end of the
eclipse respectively. Then x and y give the points where
the centre of the eclipsing body lies.
Verse 35. Given the magnitude of the eclipse at any
time to obtain the time elapsed after the first contact.
The time taken by the centre of the eclipsing body to
move through the segment of the path of the eclipsing