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

Chapter Sixteen

SAURA SIDDHĀNTA : MEAN PLANETS

१६. षोडशोऽध्यायः

सौरसिद्धान्तः — ग्रहमध्यमानयनम्

Introductory Chapter XVI of the Pañcasiddhāntikā deals with the computation of the mean star-planets, Mars etc., according to the Saura Siddhānta, and chapter XVII of their true motions, with their heliacal risings and latitudes. The mean planets are made true by employing the method of epicycles, as in the case of the Sun and the Moon, in chapters XI and X. Of the five siddhāntas condensed by Varāhamihira the Saura alone uses epicycles, and there is no evidence of its use in any other. So, in the originals also, only the Saura must have used epicycles, since VM follows the originals as far as necessary. Thus the Saura is the most mature, and may be considered to begin the highest developed stage of Hindu astronomy, represented by the Āryabhaṭīya, the Brāhma-sphuṭa-siddhānta, the Later Sūrya Siddhānta etc. Though VM's Saura, being a karaṇa, does not use yuga-cycles for the planets, the original must have had them and they can be reconstructed from the epoch-constants given, as we have done in the case of the Sun, Moon, Moon's apogee and nodes. These can be seen to agree with the corres- ponding parameters of the Pauliśa quoted by Bhaṭṭotpala in his commentary on the Bṛhatsaṁhitā, and with the Ārdharātrika-pakṣa of Āryabhaṭa, a work now lost, but reconstructible from its descrip- tion given in the Mahābhāskarīya, chapt. VII, 21-35, and from the Khaṇḍakhādyaka of Brahmagupta, which latter expressly follows the Ārdharātrika-pakṣa. Not only the yuga-cycles, but also the yuga days, and epicycles and apogee positions and nodes agree in these. Strangely enough, the 'New' Sūrya Siddhānta does not agree with the 'Old' in many things. In the matter of computing the latitudes of the star-planets, the Saura gives the same method as the Ārdharātrika-pakṣa combining two types of latitudes, but the Khaṇḍakhādyaka follows the Āryabhaṭīya itself exactly as propounded in the Mahābhāskarīya, VI. 52-55. As for agreement of VM's Saura with the other siddhāntas of the period, a perusal of the table given under XVII. 11 will show this. But it must be noted that the agreement in mere number of cycles is not real agreement, because, the yuga days being different, there will be difference in the calculated mean values. But at the period we are considering, viz. c. 500 A.D., the mean positions fairly agree with one another, and also with what would be got by modern astronomy, showing thereby the accuracy of their observations. For example, for PS's epoch, all except the later Sūrya Siddhānta give nearly 236° for Rāhu, including the moderns. This is seen only in the Rāhu of the Later Sūrya Siddhānta. (Evidently, there is error of reading here. In I.33 of the Later Sur. Sid., the original should have been vasvaśviyamāśviśikhidasrakāḥ instead of vasvagni etc. This mis-reading must have occurred before the commentator Raṅganātha, for he gives aṣṭarāmākṛtirāmadvimitāḥ. If what I suggest is correct, 3° will be added to the 232° 29' got according to the wrong reading making Rāhu = 235° 29', giving fair agreement). There is agreement in the degrees for heliacal rising and setting and the method of computing the star-planets between the Saura of the PS and the Later Sūrya Siddhānta, though the epicycles differ in many ways.