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

363 Comm. In figure 71, the eclipsing body is just con- tacting the eclipsed body. Taking the case of a lunar eclipse, the latitude then of the Moon is evidently P+r ie. β=P+r holds good at the moment of first con- tact. (C) is the cross-section of the shadow-cone at the lunar orbit and (M) is the Moon. (fig. 72), CB+AM-CM=CB+AB+ BM-CM=AB+(CB+BM)-CM= AB+CM-CM=AB ∴ P+r-β=AB=Sthagita. Thus Sthagita gives the portion of the diameter of the eclipsed body which is shadowed. The eclipsed body is termed the Chādya, the eclipsing body as the Chādaka and P+r as the Manaikya-ardha ie. half the sum ofthe diameters of the eclipsing and eclipsed bodies. Fig. 72 When the Sthagita exceeds the diameter of the eclipsed body the eclipse is evidently total ie., when P+r-β>2r ie. P-r>β. Verse 12. Duration of the eclipse and duration of its totality. Sthiti-Khanda = √(P+r)²-β² × 60 = ½ Duration of —————————————— the eclipse m₁-s₁ Marda-Khanda = √(P-r)²-β² × 60 = ½ Duration of —————————————— totality m₁-s₁ where P is the radius of the shadow-cone, r the radius of the Moon's disc, β its latitude taken to be constant during the eclipse, m₁ and s₁ the daily motions of the Moon and Sun respectively. Comm. (1) The time between the moment of first contact and the middle of the eclipse or the moment of