पृष्ठम्:चन्द्रछायागणितम्.djvu/३८

1* 14. The Great Shadow, multiplied by a gnomon of any length, and divided by the 'Great Gnomon -wim-the fifteenth part of the rate of motion of the moon per day 8 is the Correct Shadow of the moon (measured in the same unit as the gnomon used), (AlternatiYe method for the Moon's Shadow) 15. Find the product of the Bina got above (in verse 12) and the R sine of Zdn, divided by R. The difference between this and the R sine of Nati (got in verse II) is called Baku {te., base), if the Natl is of the same direction as the Zdn. If of different directions their sum (instead of their difference) is the Baku* 16. R cos latitude of the moon should be multiplied by R cos 'moon-mmi/j-Oep' and divided by R. The square root got by adding the square of this and the square of Balm is the Great Shadow. 17. The perpendicular, (/. e. t R cosine), of this, (/. e., >/(R*— Great Shadow 2 ), is the Great Gnomon. From this, the moon's, shadow of the desired time is to be got, (as before). 7 6. The purpose of subtracting the" 15th part of the daily rate of motion is to correct the Great Gnomon for parallax of the moon, which depresses the moon by about 53' in the mean near the horizon and proportionately elsewhere along the vertical circle, and lessens its apparent altitude upon which the shadow depends Hindu astronomers take the horizontal parallax proportionate to the true daily rate of motion, though this is a bit rough. 7. The second half is not clear : tf«n«T35* "The moon will be visible provided the Great Gnomon is greater than the quantity to be subtracted, (i.e., the 15th part of the daily motion, in verse 14)." Otherwise the moon will be below the horizon. This half is not commented upon by the author.