Indian Chronology (Solar, Lunar and Planetary): A Practical Guide to the Interpretation and Verification of Tithis, Nakshatras, Horoscopes and other Indian Time-records, B.C. 1 to A.D. 2000 c37: Chapter XXX. Construction of Planetary Tables XVII and XVIII
Indian Chronology (Solar, Lunar and Planetary): A Practical Guide to the Interpretation and Verification of Tithis, Nakshatras, Horoscopes and other Indian Time-records, B.C. 1 to A.D. 2000 c37
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Chapter XXX. Construction of Planetary Tables XVII and XVIII
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276. The mean sidereal periods, used in Tables XVII and XVIII, are those of modern European astronomy adjusted to the Indian sidereal year. The following table compares the sidereal period of each planet, ordinarily given in Indian astronomical works, with that adopted in this work as well as with the results of modern astronomy.
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| Planet. | Indian Sidereal period. | Modern Astronomy (Encycl. Brit.) | Figure adopted in this work. |
| | Days. | Days. | Days. |
| Mars | 686·99749 | 686·979645 | 686·98814 |
| Mercury | 87·969702 | 87·969258 | 87·96939 |
| Jupiter | 4332·3206 | 4332·584821 | 4332·92322 |
| Venus | 224·698568 | 224·700786 | 224·70169 |
| Saturn | 10765·7730 | 10759·219817 | 10761·30664 |
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277. In the first place it was thought unnecessary to observe in regard to planetary sidereal periods the same scrupulous adherence to Indian authorities which is incumbent in the case of the solar year and the moon's synodical month. In the next place, the difference in the length of the sidereal year between Indian and modern astronomy results in a slight displacement of the starting point of Indian celestial longitude, which displacement amounts to 7' 6·26"
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in 50 years and should be added to the precession, amounting, according to modern astronomy, to 41' 52·27" for fifty years. The total difference between Indian sidereal and modern tropical longitudes is thus 48' 58·53" for 50 years or 59" per annum, while Bhâskara's estimate of the precession, 59·9007" per annum, is only slightly larger.
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278. If the slight annual displacement of the zero point of Indian longitudes, which is a practical postulate of Indian astronomy, however unrecognized in theory, is applied to the sidereal places of planets, their mean sidereal periods will have to be altered as shown above. In this manner alone will it be possible to apply to the planets the same precession as is applied to the sun, for the purpose of converting sidereal into tropical longitude.
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N.B.—By taking this slight liberty with the mean sidereal periods of planets, the exact agreement of the mean place of any planet with its place in modern astronomy is secured, and the serious divergences between the two systems, commented on in Whitney's notes on the Surya Siddhanta have been effectually avoided. As a result, the place, whether mean or actual, assigned to any planet in Tables XVII and XVIII, may not tally exactly with Indian calculations, but the difference will generally be found to be very slight, while there is an obvious advantage in having for every possible epoch a mean place for each planet, identical with that assigned to it by modern astronomy.
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279. The planetary anomalies and annual equations, which were used for Tables XVII and XVIII of this work, were taken from Warren's Kâla Sankalita and are ascribed by that author to a local Telugu Astronomer of the time, called Vavilâla Kuchinna. The tables are no doubt old-fashioned, but they are handy and sufficiently accurate for the purposes of Indian horoscope-chronology. This is the main reason for resuscitating them into present-day use.
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280. The figures as to longitudes of apses and nodes and the greatest apparent latitudes of planets (Table XVII) are taken, partly from Warren and partly from the Siddhânta Siromani.