90 VISIBILITY j PHASES AND RISING OF THE MOON [CH. VI asus denote the second approximation to the time between moonrise and sun- set. Repeat the above process successively until the successive approximations to the time between moonrise and sunset agree. The time finally obtained, gives the time of moonrise before sunset. This being subtracted from {he du- ration of the day gives the time of moonrise as measured since sunrise, A rule relating to the time of rising of the Moon on the full moon day : 20-21- If (at sunset) on the full moon day the longitude of the Moon (corrected for the visibility corrections) agrees to mi- nutes with the longitude of the Sun (increased by six signs), then the Moon rises simultaneously with sunset. If (the longitude of the Moon is) less (than the other), the Moon rises earlier; if (the longitude of the Moon is) greater (than the other), the Moon rises later. (In the latter cases) multiply the minutes of the difference by the asus of the oblique ascension of the sign occupied by the Moon and divide by the number of minutes of are in a sign, and on the resulting time apply the method of successive approxima- tions (and get the nearest approximation to the time to elapse at moonrise before sunset or elapsed at moonrise since sunset). 1 When the longitude of the Moon is less than the longitude of the rising point of ecliptic (at sunset), the process of successive approximations will be similar to that explained under stanza 19 above while dealing with Sankara- narayana's interpretation; when the longitude of the Moon is greater, the pro- cess of successive approximations will be similar to that explained below in stanzas 23-25. A rule relating to the determination of the shadow of the gnomon due to the Moon: 22- From the asus { of the oblique ascension of the portion the ecliptic) lying between the rising point of the ecliptic and
- the Moon (corrected for the visibility corrections) or from those
(taken in setting at the local place by the portion of the ecliptic) lying between the setting point of the ecliptic and the M 1 Cf. MBh, v. 22.
