What is "drigganita"

Drigganita, also called the Drik system, is a system of astronomical computations followed by several traditional astronomers, astrologers and almanac makers in India. In this system the computations are performed using certain basic constants derived from observations of astronomical phenomena. The almanacs computed using the methods of Drigganita are referred to as Drigganita Panchngas. In Tamil speaking world, they are also known as Thiru-ganita Panchangas.

The Drigganita system is in contrast to the method followed by some other almanac makers who use the values given in the ancient astronomical treatise known by the name Surya Siddhanta. The almanacs computed using this treatise are known as Sydhantic Panchangas. They are also known as Vakya Panchangas.

In the history of astronomy in India, two different Drigganita systems have been introduced at two different points of time and at two different geographical locations. The first system was introduced by the Kerala astronomer-mathematician Parameshvara (1380-1460) in the fifteenth century. Incidentally, Drigganita is also the title of a book authored by Parameshvara through which the Drik system was promulgated. In the nineteenth century, a second Drigganita system was introduced by Chinthamani Ragoonatha Chary (1822 – February 5, 1880) an Indian astronomer attached to the then Madras Observatory.