पञ्चसिद्धान्तिका (आचार्य वराहमिहिर - सूर्य, रोमक, पौलिश, वासिष्ठ एवं पितामह सिद्धान्त)

XI.3 XI. ECLIPSE DIAGRAM 237 सत्रिगृहस्य हिमांशोरपक्रमांशान् यथादिशं कुर्यात् । प्रागपरसिद्धिरवेवं (चक्रा)द् याम्योत्तरे ज्ञेये ॥ ३ ॥ 3. Add three rāśis to the Moon’s longitude and find the degrees of declina- tion of this point. If the declination is north, lay the degrees north of Eʹ, if south, south of Eʹ. This is the east-point with respect to the ecliptic (E″ in the figure.) Draw the straight line through the centre, E″ OW″ . E″ – W″ is the ecliptic east-west. By means of circles, (i.e. by drawing the perpendicular bisector), get the ecliptic north-south, viz. N″ – S″. [Diagram: Fig. XI.1 showing celestial/ecliptic circles with points N, N″, S, S″, E, Eʹ, E″, W, Wʹ, W″, O, A, b, f, fʹ, l, lʹ, s, w, "Eclipsed Circle", and "Sum-Circle"] Fig. XI.1 For illustration, we shall represent in the figure the lunar eclipse worked out in the examples of chap. X. The angular diameters of the Moon and the Shadow got there are 31ʹ.8 and 76ʹ.9. The Moon’s lat. at first and last contacts are, respectively, 19ʹ.35 and 27ʹ.65, both north. The first and second half durations are nā. 4-14 and nā. 3-54, respectively. Let us assume that at T, the hour angle, is 10 nāḍīs, i.e. 60°, west and the latitude of the observer is 10° 24ʹ (N). The Moon’s longitude has already been given as rā.4-0-0. (i) The half sum of the angular diameters = 108ʹ. 7 ÷ 2 = 54ʹ.35. This is to be converted into digits using the formula of verse 6, below, and used as the radius of the sum-circle. It is, 54.35 ÷ (3 – 10/15) = 23.3 digits. According to the scale in the figure, 1 unit = 10 digits, this is 2″.33. 3b. B. ॰मांशात् द्यथा c. A. सिधिरेवं. C. मत्स्याद्; D. बकाद् d. A.B. वकाद् A. याम्यान्तरे; B. याम्योतर D. ज्ञेये [च]