177 THE DIAMETER OF THE SHADOW (2) ECLIPSE OF THE MOON Points of difference of procedure in the case of a lunar eclipse: 68-70. Similarly, in the case of the Moon, which is the mirror for the face of the directions and exhibits (or bears) all excellent phases and whose round body looks like the face of a damsel, too, the (ten) Rsines should be found out. The points of difference (in the procedure) are being stated. The (five) Rsines relating to the shadow should be deter- mined as arising from the Sun's orbit. (In plac of the Sun's distance) the Moon's distance is stated to be the divisor. The lambana, determined as in the case of the Sun, should be added or subtracted reversely. Use of parallax in a lunar eclipse prescribed in the above stanzas is obviously wrong. Parameśvara comments: "Thus in the case of a lunar eclipse also, the use of parallax is stated here. This, say the profi- cients in Spherics, is improper". It must be mentioned that the application of parallax in the case of a lunar eclipse has not been prescribed in any other work on Hindu astronomy, not even in the smaller work of the present author. A rule for the determination of the diameter of the shadow, i.e., the diameter of the section of the Earth's shadow where the Moon crosses it : 71-73. Multiply the Sun's (true) distance in yojanas by the Earth's diameter and divide by the difference of their diameters: thus is obtained the length of the Earth's shadow. Or, multiply the Sun's (true) distance in yojanas by 5 and divide by 16: the result is called the length of the Earth's shadow, From that (length of the Earth's shadow) subtract the Moon's distance. Multiply the remainder by the Earth's dia- meter and divide (the product) by the length of the (Earth's) shadow. Multiply the resulting quotient by the radius and divide (the product) by the Moon's distance (in yojanas): this is (the diameter of) the shadow (in minutes of arc).
