ELEVATION OF THE LUNAR HORNS 193 A rule telling how many nadis before or after sunset will the Moon be seen to rise on the full Moon day: 22. Diminish the nadis (due to the oblique ascension of the part of the ecliptic) intervening between the Sun and the (visible) Moon (at sunset on the full moon day) (from or) by (the nadis of) the length of the day: so many nadis before or after sunset is the Moon seen (to rise on the full moon day).¹ A rule relating to the representation of the elevation of the lunar horns in the dark half of the month: 23-25. After the end of the (light) fortnight, the Moon, lying above the horizon, is drawn by using the measure (of the Rsine of the Moon's altitude) computed from (the asus due to the oblique ascension of the part of the ecliptic intervening between the visible Moon and) the rising point of the ecliptic at the given time. The upright is laid off towards the west³; the base is laid off along the north-south line (in its proper direction); and the hypotenuse-line is stretched out from the end of that (base) to meet the end of the upright. Then from the east point (of the Moon's figure) lay off the measure of the (Moon's) illuminated part along the hypotenuse-line within the figure of the Moon; or, from the west point (of the Moon's figure), lay off the (measure of the Moon's) unilluminated part. A rule telling how to do the same at sunrise in the dark half of the month : 26. Or, perform the operation, stated above, concerning the Moon's illuminated or unilluminated part at sunrise with the asus intervening between the (visible) Moon and the Sun at that time. The time of moonrise will now be told. 1 This rule gives an approximate time of moonrise. In order to obtain the nearest approximation to the correct time of moonrise use should be made of the method of successive approximations. See infra s tanzas 31-35.
- Because in the dark fortnight the Moon is to the west of the Sun,
