SUN'S ALTITUDE The correct formula is Rsin a Rsin x Rsin (L-S) R where denotes the altitude of the central ecliptic point.¹ 77 The author does not prescribe this correct formula, because the value of Rsin has not been accurately determined by him. In Chapter V he gives only an approximate formula for it." For practical purposes the approximate formula is good enough. Definition of "the upright due to the meridian-ecliptic point:" 22. The square root of the difference between the squares of the Rsine of the zenith distance of the meridian-ecliptic point and of the radius (ravi-kaksya) is called "the upright due to the meridian-ecliptic point" by those who are well versed in Spherics. Thus we see that "the upright due to the meridian-ecliptic point" is the Rsine of the altitude of the meridian-ecliptic point. It is usually called madhya-śanku. The word ravi-kakṣyā, literally meaning "the Sun's orbit", is used in the text in the sense of "the radius (of the Sun's orbit)". Two alternative rules for finding the Sun's altitude : 23-24. Increase or diminish the ghatis (elapsed since sunrise in the forenoon or to elapse before sunset in the after- noon) by the asus of the (Sun's) ascensional difference (according as the Sun is in the southern or northern hemis- phere). To the Rsine of that apply the Rsine of the (Sun's) ascensional difference reversely to the above. By what ¹ The central ecliptic point (also called the "nonagesimal") is that point of the ecliptic which is 90 degrees behind the rising point of the ecliptic and 90 degrees ahead of the setting point of the ecliptic. This point of the ecliptic is at the shortest distance from the zenith and is the central point of that part of the ecliptic which lies above the horizon. 2 See infra, Chapter V, verse 19.
