191 ELEVATION OF THE LUNAR HORNS hypotenuse is the east-west line of that (Moon's disc); through the middle of that (i.e., through the centre of the Moon's disc) draw the north-south line. At the extremities of the north-south line mark two points on the periphery of the Moon's disc. (Then lay off the Moon's illuminated part) along the hypotenuse (from the west point) towards the interior of the Moon's disc and mark there the point of illumination. Thereafter always draw a circle passing through the (above-mentioned) three points. The portion lying between that (circle) and the (periphery of the) Moon's disc (lying towards the Sun) is called the illumi- nated part (of the Moon). The elevation, depression, or horizon- talness of the Moon's horns, in whatever unit be it measured (in the figure), is clearly perceived in the sky (as in the figure).¹ In Fig. 23, AB is the base and MA the upright. Then, according to Bhaskara I, B denotes the Sun's centre and M the Moon's centre. The circle NESW centred at M is the Moon's disc, the points N, E, S, and W being the north, east, south, and west points on its periphery. The measure of the illuminated part of the Moon, IW, is laid off from W to- wards M and an arc of a circle is drawn through N, I, and S.² The shaded portion lying bet- ween this arc and the arc NWS is the illuminated part of the Moon's disc. The cusps at N and S are called the Moon's horns. The figure shows that in the present case the case the northern horn is higher than the southern one, E Fig. 23 Representation of the elevation of the lunar horns at any other time instead of sunset in the first quarter of the month : 18. This (above) method is to be followed at sunset. At (any other) given time, all calculations such as the determination ¹ This rule is approximate. For other rules, see BrSpSi, vii. 7-10; SiDVṛ, I, ix; Sisi. I, ix.
- The point I is called "the point of illumination" (sitabindu).
