88 VISIBILITY, PHASES AND RISING OF THE MOON [CH. VI and tail of the fish-figure constructed at the end (of the base). (This) perpendicular should be taken equal to the Rsine of the Moon's altitude and should be laid off towards the east. The hypotenuse-line should (then) be drawn by joining the ends of that (perpendicular) and the base. TheMoonis (then) constructed with the meeting point of the hypotenuse and the perpendicular as centre; and along the hypo- tenuse (from the point where it intersects the Moon's circle) is laid off the measure of illumination towards the interior of the Moon. The hypotenuse (indicates) the east and west directions : the north and south directions should be determined by means of a fish-figure. (Thus are obtained the three points, viz.) the north point, the south point, and a third point obtained' by lay- ing off the measure of illumination. (Then) with the help of two fish-figures constructed by the method known as tri'sarkaravidhana draw the circle passing through the (above) three points. Thus is shown, by the eleva- tion of the lunar horns which are illumined by the light between two circles, the Moon which destroys the mound of darkness by her bundle of light. 1 Exhibition of the lunar horns in the second quarter of the month : 18. (When the Moon is) in the eastern half of the calestial sphere, the true base should be found out with the help of the rising point of the ecliptic and the Moon's agra, etc.; and the un- mentioned element (i.e., the upright) should be laid off towards the west 2 The true base here corresponds to the base of stanza 11. A rule for finding the duration of visibility of the Moon in the light half of the month : 19. The nadts (of oblique ascension of the portion of the ecliptic) intervening between the Sun and the Moon 3 (at 1 Cf. MBh, vi. 13-17. 2 Cf. MBh,v. 19. 3 Corrected for the visibility corrections.
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