Synopsis Predictive astrology is based on the positions of planets, ascendant, expansion of bhavas etc. at the time of birth of a native or question. Horoscope, Chalit charts and Divisional charts are casted for that time. Now-a-days these are generated by use of computer. Sometimes mistake may appear due to programming error or some defect in the computer, so it is very essential for an astrologer to have the knowledge to check the corrections and accuracy of horoscope and other charts.

An astrologer must have preliminary knowledge of astronomy. These days normally astrologers do not observe the planets and other celestial bodies but use the longitudes, latitudes, declinations etc. observed by the observatories or calculated by traditional methods. Astrology is an experimental science and thus a very small error may cumulate to a big difference in several hundred years. So our traditional methods require some correction.