VS 23-25] MOON IN THE DARK FORTNIGHT 91 (corrected for the visibility corrections) (according as the Moon is above the eastern or western horizon), and from the Moon's day radius, etc , determine (the Rsine of) the (Moon's) altitude and zenith distance and therefiom the shadow' of the gnomon (due to the Moon) 1 . A rule for finding the time of moonrise in the dark half of the month: 23-25. Multiply the minutes of arcof the rising sign to be traversed by therising point of the ecliptic at sunset by the oblique ascension of thatsign and divide by the number of minutes of arc in a sign: thus are obtained the asus (of the oblique ascension of that part of the rising sign which is below the horizon). Adding thereto the asus (of the oblique ascension) of the succeeding portion of the ecliptic traversed by the Moon calculated for sunset up to the last minute of arc (of her longitude), find out the Moon's motion corresponding to that time by proportion, and add that to the longitude of the Moon. Then by repeating the above process again and again find the nearest approximation to the time between sunset and moonrise. After the lapse of that time during night, in the dark half of the month, is seen to rise the Moon who by her rays of light has destroyed the mound of darkness. 3 The time obtained above is in sidereal reckoning. If the use of the Sun's displacement is also made at every stage, the resulting time would be in civil reckoning. 1 See supra, Chapter iii, stanzas 7-10, 11. 2 Corrected for the visibility corrections, 3 Cf. MBh, vi. 28-31.
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