The traditional calculation system for Jung Tsee and Kar Tsee is based upon the text called rig den nying thig which is the main source for astronomical calculations, ie Kar Tsee, but also calculates the calendar which underlies the Jung Tsee system. This is neither a sidereal zodiac using any ayanamsa, nor is it tropical as we know that system today. The results of this calculation would seem quite surprising to modern astrologers and astronomers. The method for calculation employs a tradtional practice using a sand tray board called the 'sa gzhong'. The method therefore often requires placing results in various corners/sides of the board and does not use calculus nor modern mathematical algebraical functions. As such it is an algorithm based upon tradition and whilst some believe that it became inaccruate over the centuries, none-the-less it remains the official system of calculating the calendar. This of course is one of the controversial issues in Tibetan Astrology today.
The Tibetan system of astronomy divides the great circle into 1620 astron hours, which is quite different to our western 360 degrees.
Calculations are of two types called:
a. Siddhanta system (dub pa) pron Du-ba
this type of calculation can be termed the full tenet system and calculations are made from first principles of Kalacakra astronomy.
b. Karana system (byed pa) pron Jay-ba
this type of calculation can be termed the precise system (or shortened system) because it requires less calculation time.
For a really detailed example of the traditional method of calculation click here. NB. 48K.
Other calcualtions files -