The chosen deity
The ishta devata is the form of the divine a person is understood to be most naturally drawn to. In Jaimini astrology it is read from the twelfth house from the Atmakaraka in the navamsa — the twelfth being the house of liberation, and the Atmakaraka being the planet holding the highest degree in the chart.
The Atmakaraka
Atmakaraka means significator of the soul. It is determined purely by degree: whichever of the seven planets sits furthest through its sign takes the role, regardless of which sign or house that is. It is read as the matter a life is most concerned with.
How it is used
The ishta devata is a direction for practice rather than a prescription. It suggests where devotion is likely to come naturally and where it is said to bear fruit fastest, and it is traditionally confirmed by a teacher rather than settled by a calculation alone.
Common questions
What is an Atmakaraka?
The planet at the highest degree within its sign, regardless of which sign or house. Its name means significator of the soul, and it is read as the matter a life is most concerned with.
Must I worship only this deity?
No. The ishta devata indicates where devotion is likely to come naturally, not a restriction on anything else. It is traditionally confirmed by a teacher rather than settled by calculation alone.