jyotisha directs auspicious moments for starting any karma or yajna, based on the location, combination, and influence on each other of the celestial bodies such as grahas, soorya, chandra etc., stars and other celestial bodies.

Any karma that is performed with good procedure and on an auspicious muhoorta based on good tithi, vaara, nakshatra and lagna only will yield good results. purohits mention this in principle.

Every yajna has a fixed time to perform, based on season, month, fortnight, and day. Checking the time and doing timely takes important role.  To decide the auspicious time jyotisha vidyaa was developed. In chaandogyopanishat it is named as daiva nakshatravidya.

There are two jyotishas, rugveda jyotisha with 44 shlokas and yajurveda jyotisha with 36 shlokas. jyotisha grantha written by lagadha is considered as root for the above two jyotishas. He is considered as from kashmir or present Afghanisthaan. Timing of this grantha is expected to be 1181BC as per William Jones, and 1391BC as per Dilees, Kol Brook, and 1400-1200BC as per Tilak.

Later granthas were written by aaryabhatta, varaaha mihira, brahmaa gupta, bhaaskaraacharya.  jyotisha further expanded as samhita bhaaga, ganita bhaaga and jaataka bhaaga. The granthas poorva kaalaamruta, uttara kaalaamruta, bruhat samhita etc are some of  jyotisha granthas.