Bharatiya Jyotihshastra (History of Indian Astronomy), translated by R. V. Vaidya v2.c14.33

v2.c14.33

If the knowledge of astrology dates as far back as 5 centuries before Śaka era, the system of mathematical branch of astronomy must have been equally ancient, because, no astrological consideraion is possible, unless the positions of planets in signs are known and the earlier discussion has shown that there is no reason for presuming that the branch of astronomy had not reached such maturity in such a remote period of antiquity. Moreover, it must be remembered that even though the mathematical branch had not been completely mastered, in other words even though the knowledge of true places and motions of planets was not attained, the ancients at least knew the mean motions and positions of planets and had undoubtedly attained before 500 B.S. a general knowledge of the sign positions of planets (p. 127 and 146 of pt. I). Even if the true positions and motions of planets cannot be correctly found by calculation, the naked eye can at least show where the planet is in the sky, when it becomes direct or retrograde, when it rose or set heliacally. So then the knowledge of mathematics need not necessarily have reached maturity when the present system of astrology came into vogue in this country. The reason why planetary motions were considered in our country and the science of astronomy reached perfection (of course, within the limits of our ancient works) and remained alive till today lies mainly in the necessity to judge the possible effects of the movements of planets. The works on Saṃhitā describe the effects of planetary movements. The desire to foresee these effects, the need of auspicious moments for sacrifices or other rites and the effects of planetary movements on each person as in natal astrology are the three reasons why the science of astronomy originated in this country, developed to a considerable extent and continued to exist. (In Europe, the main cause of its reaching a very high degree of development as at present was navigation. Still even there these yery three things were mainly instrumental in the past in bringing the science to the same stage of development as in India). It is, therefore, evident that the present system of astrology must have been established before the science of astronomy attained ‘its’ full status; that is, before the correct knowledge of finding true positions and motions of planets could be attained. Hence one cannot lightly dismiss as improbable the view that the present system of astrology became established in our country four or five centuries before Śaka era.