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vs 12(ii)-17] EXHIBITION OF LUNAR HORNS 87 ence is the corresponding time, i.e., the time that the Maon take? in moving from the equatorial horizon to the local horizon. The Moon's sahkvagra is the distance of the foot of the perpendicular dropped from the Moon on the plane of the horizon, from the rising-setting Jine of the Moon. The methods of finding the Moon's earthsine, ascensional difference, alti- tude and sahkvagra are similar to those for the Sun. A rule relating to the determination of the Moon's true decli- nation and the Moon's agra : 9-10. The Rsine of the difference or sum of the (Moon's) latitude and declination according as they are of unlike or like directions is (the Rsine of) the Moon's true declination. 1 From that (Rsine of the Moon's true declination) determine her day- radius, etc. Then multiply (the Rsine of) the Moon's (true) declination by the radius and divide by (the Rsine of) the colati- tude : then is obtained (the Rsine of) the Moon's agra. 2 The true declination of the Moon means the declination of the centre of the Moon's disc. The Rsine of the Moon's agra is the distance between the east-west line and the Moon's rising-setting line. A rule relating to the determination of the base (bahu) : ll-12(i). If that (Rsine of the Moon's agra)- is of the same direction as the (Moon's) sahkvagra, take their sum ; otherwise, take their difference. Thereafter take the difference of (the Rsine of) the Sun's agra and that (sum or difference) if their directions are the same, otherwise take their sum : thus is obtain- ed the base {bahu). 3 Construction of the figure exhibiting the elevation of the lunar horns in the first quarter of the month at sunset : 12(ii)-17. Lay that (base) off from the Sun in its own direc- tion. (Then) draw a perpendicular line passing through the head 1 Cf. MBh, vi. 8. a Gf. MBh, vi. 10-1 l(i). 8 Cf. MBh, vi. ll(ii)-12.