Astronomy is the basis of Astrology, and as the Śāstras state, Siddhānta is the mathematical component of Jyotiṣa. One must study the Siddhānta to understand how the ancient Maharṣis and Ācāryas computed the Graha positions. Learning the evolution and history of a subject is as much important as the current state of the subject. The knowledge of computation of planetary positions in the sky is only a starting point in the entire field of astronomy. After covering the method of determining the Longitude and Latitude of a Graha, Sūryasiddhānta moves on to apply that in ascertaining astronomical events such as Yuti (conjunction), Astāṅgata (combustion), Grahayuddha (planetary fights), Vakragati (retrogression), Grahaṇa (eclipse) and several others. This book explores the astronomical and astrological aspects of such events. Also covered are an introduction to Aṅkaśāstra, or Vedic Numerology, which is based on the Year, Month, Day and Horā lord. Siddhānta texts lay down the principles of determining them but are hardly used today. I hope this book will serve as a guide to the mathematical-minded Jyotiṣīs to Astronomical aspects of Jyotiṣa.
