Bharatiya Jyotihshastra (History of Indian Astronomy), translated by R. V. Vaidya v2.c12.s2.t85.4

v2.c12.s2.t85.4

Veṅkateś compiled a very useful work in Sanskrit, entitled "Jyotirgaṇita" about Śaka 1812. He has adopted in it, Śaka 1800 as the epochal year. This has been compiled on the basis of those French works which are being used in compiling the Nautical Almanac. The planets' places, calculated with the help of this work, are very accurate, in fact they are correct within 1' as compared with those of the Nautical Almanac. Never before has such a work been compiled in this province, not even in our country. This work has adopted for the length of the year the correct value of the sidereal year viz. 365d-15-22-53 and 50''.2 (the actual value) as the annual rate of precession. Assuming Zeeta Piscium to be the junction star of Revatī, he has given its sā yana longitude, or in other words, the ayanāmśa for the Śaka year 1800 as 18° 10' 25''. The author had suggested to him to adopt for the ayanāmśa a figure approximately equal to that of the Grahalāghava. A star whose longitude would be equal to it could have been adopted as the initial point. But even Ketkar has come to realise the fact that the ayanāmśas can be nearly equal to those of Grahalāghava, by assuming 180° as the longitude of the star Citrā (Spica). In short, if he had assumed 22° as the aproximate ayanāmśa for Śaka 1800, the author feels that Ketkar's work would have easily come into general use. The work mainly consists of four parts. The first contains the calculation of the almanac. The epochal positions are all given for the moment of the true Aries Ingress. The second part treats of the calculation of the places of planets. It includes the mean and true longitudes of planets, the right ascension, longitudes of star etc., heliacal rising and setting of celestial bodies, and other subjects. The third contains the calculation of phenomena like eclipses, conjunctions, elevtaion of moon's cusps. The fourth contains the calculation of the ascendant etc. required in the case of three problems. The treatment of each subject has, everywhere in the book, adhered to the following order :-Method, example, tables and then the theory. The work contains tables for almost all calculations, and the calculators who do not understand the use of trigonometry and longarithms can easily make calculations from the book. Keropant's almanac can be compiled with the help of this Book. This book has not been printed as yet.