. CHAPTER VI RISING, SETTING AND CONJUNCTION OF PLANETS. A rule relating to the visibility-correction known as aksa- drkkarma : 1-2(i). Multiply the Moon's latitude for the desired time by the Rsine of latitude of the local place, and divide (the product) by the Rsine of the colatitude; whatever is thus obtained, say the learned, should be subtracted (from the Moon's longitude) in the case of rising of the Moon (i.e., in the eastern hemisphere) and added (to the Moon's longitude) in the case of setting of the Moon (i.e., in the western hemisphere), provided that the Moon is to the north of the ecliptic (i.e., if the Moon's latitude is north). When the Moon is to the south of the ecliptic, the law (of addition and subtraction) is the reverse.¹ The correction stated in the first three stanzas of this chapter is called "the visibility-correction (drk-karma)". When we apply this correc- tion to the true longitude of the Moon, we obtain the longitude of that point of the ecliptic which rises or sets with the apparent Moon. The visibility-correction is generally broken up into two compo- nents: (1) the visibility-correction due to the latitude of the local place (akşa-drkkarma), and (2) the visibility-correction due to the Sun's northward or southward course (i.e., ecliptic-deviation) (ayana-dṛkkarma). Let Fig. 21 represent the celestial sphere for the local place. SEN is the eastern horizon and Z the zenith; TE is the equator and P its north pole; TT is the ecliptic and K its north pole. Suppose that the Moon is rising at the point M' on the horizon. Let M be the point where the secondary to the ecliptic (kadambaprota-vṛtta) drawn through M' intersects the ecliptic, L the point where the hour circle (dhruvaprota-vṛtta) ¹ The same rule is found to occur in BrSpSi, vi. 4; Ś¡DVŢ, I, vii. 3 (ii); M.Si, vii. 4 ; Sise, ix. 7.
