पञ्चसिद्धान्तिका (आचार्य वराहमिहिर - सूर्य, रोमक, पौलिश, वासिष्ठ एवं पितामह सिद्धान्त)

138 PAÑCASIDDHĀNTIKĀ V. 3 दिनकृत्सप्तमभवनात्तेनोदयनाडिकाद्वयं यदि वा | वियति विमले (तदे)न्दोर्लोकस्यालोक (आ)याति || ३ || 3. In the case of the visibility pertaining to the west, if a segment equal to the corrected difference in longitude takes at least two nāḍīs to rise in the east as reckoned by using the ascensional difference (for the place) of the seventh rāśi from the Sun, then the Moon will be visible, provided the sky is clear. In the case of visibility in the east, use the ascensional difference of the Sun’s rāśi itself. The following are the steps in the operation:- i. Find the difference in the longitude of the Sun and the Moon. ii. Find the difference of the Sun’s declination, and the Moon’s mean declination. iii. The square root = √[(diff. in long. + diff. in dec.) × (diff. in long. − diff. in dec.)] iv. Result = diff. in dec. × Moon’s lat ÷ the square root. v. Corrected diff. in long = diff. in long ∓ result. (Of ∓ the upper sign is to be used if visibility pertains to the west, and the latitude and the course of the Moon are of the same direction, or if the visibility pertains to the east and the latitude and course of the Moon are of different directions. The lower sign is to be used otherwise. vi. If the visibility pertains to the west, find the time of rising of an ecliptic segment equal to (v), by using the ascensional difference (for the place) of the seventh sign from the Sun and Moon. If it pertains to the east, use the ascensional difference of the Sun’s rāśi itself. If the time so found is greater than two nāḍīs, the Moon is visible; otherwise it is not visible. The time that we find in (vi) is the time of Moonset after sunset in the west, and the time of moon- rise before sunrise in the east. The sun, Moon, declinations and latitude of these times should be used and the work repeated for greater accuracy. Other siddhāntas mention this, though the author here has not done so specifically. Or, even before beginning the work, we can know the approximate times of moonset and moonrise, and do the work using the elements of these times. Near the time of new moon the Moon is invisible because the lighted up part is very small, and the sky itself is bright by the nearness of the Sun below the horizon. It has been fixed by the ancient authors by observation, that if the Moon sets within two nāḍīs after sunset, or if the sun rises within two nāḍīs after moonrise, the moon is not visible. (In places near the equator this criterion will be satisfied if the elongation of the Moon is in the neighbourhood of twelve degrees.) It is this we are finding by the computation, and it is obvious that the nearer the time of the elements used to the result, the better will be the result itself. Therefore is the need for successive approximation. If it is only for the sheer beauty of its appearance in the sky which has been described by poets like Kālidāsa, the first digit of the Moon is fit to be sought. But it is necessary for religious purposes 3b. A. ॰नोदया. c.A. तदिन्दो d. A.C.D. U. लोकमायाति ।