186 A rule relating to the visibility of the Moon: 4-5(i). The Moon's longitude, which is obtained in this way after the application of the above-mentioned (visibility) corrections, is stated by the learned to be the longitude of the visible Moon (i.e., the longitude of that point of the ecliptic which rises with the Moon). RISING, SETTING AND CONJUNCTION OF PLANETS When the pranas¹ (of the oblique ascension) due to the degrees intervening between the Sun and the (visible) Moon,³ reduced to ghatis, amount to two, then the Moon is seen to rise in the clear, cloudless, starry sky after sunset.³ The latter part of the above passage relates to the visibility of the Moon, or, in other words, the heliacal rising of the Moon. On the fifteenth lunar day of the dark half of the month, the Moon comes near the Sun from behind and is lost in his splendour. After about two days it is beyond the limit of invisibility and is again seen in the sky after sunset, being in advance of the Sun. In order to see whether the Moon will be visible on the first or second lunar day of the light half of the month, one should calculate the (sayana) longitude of the Sun for sunset on that day and also the (sayana) longitude of the Moon corrected for the visibility corrections for the same time. If the oblique ascension of the part of the ecliptic lying between the Sun and the Moon thus obtained is equal to or greater than two ghatis, the Moon will be visible (after sunset that day, otherwise not. Similarly, in order to test whether the Moon will be visible in the night just (before she sets heliacally) on the fourteenth or fifteenth lunar day of the dark half of the lunar month, one should calculate the (sāyana) longitude of the Sun for sunrise following that night and also the (sayana) longitude of the Moon corrected for the visibility corrections for the same time. If the oblique ascension of the part of the ecliptic lying between the Sun and the Moon thus obtained is equal to or greater than two ghatis, the Moon will be seen before sunrise, otherwise not. 1 Prāṇa is the same as asu. • Both sayana. 3 This rule is found to occur also in PSi, v. 3; BrSpSi, vi. 6; x. 32; SiDV, 1, vii. 5; Siśe, ix. 8(i), 13,
