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

91 begins simultaneously for any place of the earth, if y > x, then he should know that he lies on the east of the primary meridian because his Sun-rise happens to be earlier than the Sun-rise on the primary meridian. Also the difference y—x gives the Desāntara correction in time for his place. The converse is the case if he happens to lie on the western side of the primary meridian. The time at which the eclipse takes place on the primary meridian after the Sun- rise there which is obtained by computation is called Drik- grahaṇa - Kāla ; whereas the local time after Sun-rise observed by the observer is called pragrahaṇa-Kāla. Their difference is therefore the Desāntara correction in time. If the Desāntara is to be got in yojanas, (T × C) / 60 is the answer, where T=y—x and C is the rectified circumference of the earth, for, if a difference of 60 ghaṭis be there for C yojanas, what should be the distance in yojanas in order that the difference is T”? The answer is as given above. Hence to obtain the positions of the Sun and the Moon at the beginning of the eclipse at the locality we have to add or substract as the case may be (T × δm) / 60 where δm is the daily motion of the Sun or the Moon, and T is y—x cited above, for, “ If in 60 ghaṭis the motion be δm, what would it be in T ?” is the rule of three for which the answer is as stated above. Now the question is when the week-day begins for the locality. It must be noted clearly, that in Hindu Astro- nomy the moment of Sun-rise at the primary meridian alone is to be reckoned as the beginning of the week-day universally. This convention is adopted for convenience. Thus the astronomical week day for any locality does not begin from the Sun-rise of the locality, but may begin earlier or later. This difference is given by y — x cited above.