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

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when the lunar orbit comes in between the celestial
Equator and the ecliptic. This situation, in its turn,
depends upon the position of Rāhu. Since Rāhu's sidereal
period amounts to nearly 18½ years, the lunar orbit
happens to take its position in between the celestial
Equator and the Ecliptic for sufficiently a long period as
shown below.
That Bhāskara could visualize this, reflects credit
to his genius. This is why he formulated Δδ ± Δβ
stressing upon the plus or minus sign.
Fig. 128
Bhāskara gives an example under the above verse
in the commentary to justify his finding given above.
Suppose Rāhu is at the autumnal equinox and the longi-
tudes of both the Sun and the Moon are equal to 79°.
Adding the Ayanāṁs'as 11°, their longitudes are each 90°
so that both of them are at the summer solstice ie. an
Āyana Sandhi. (Of course the Moon is not exactly at the
position of the Sun, but he being in his own orbit, his
longitude measured along the Ecliptic is 90°). Then
evidently the lunar orbit lies in between the celestial
equator and tho Ecliptic. Then the declination of the
Moon is 24°–4½°＝19½°＝1170′ and the declination of the
Sun is 24°＝1440′. Thus the Moon's declination when
it is maximum falls short of that of the Sun. After half
of the sidereal period of the Moon namely 13⅔ days, the