Jyotiṣa — the eye of the Veda

ज्योतिष

Also written: jyotisha · vedic astrology · jyotish · nakshatra · vedanga jyotisha · ज्योतिष

Jyotiṣa is called the eye of the Veda because it tells you when. A rite performed with perfect procedure at the wrong moment is, in the tradition's view, a rite performed into the wind. Its original purpose is the calendar; everything else grew from that.

The oldest surviving text of the limb, Lagadha's Vedāṅga Jyotiṣa, states its own rank in an image and then justifies the rank with an argument.

यथा शिखा मयूराणां नागानां मणयो यथा। तद्वद्वेदाङ्गशास्त्राणां ज्योतिषं मूर्ध्नि संस्थितम्॥

yathā śikhā mayūrāṇāṁ nāgānāṁ maṇayo yathā tadvad vedāṅga-śāstrāṇāṁ jyotiṣaṁ mūrdhni saṁsthitam

As are the crests on the heads of peacocks, as are the gems on the hoods of serpents, so does astronomy stand at the head of the sciences that are the limbs of the Veda.

— Lagadha, Vedāṅga Jyotiṣa 4 (Ārca recension; = 35 in the Yājuṣa recension)

The argument follows immediately, and it is the whole rationale of Indian astronomy: the Vedas exist for the sake of sacrifice, sacrifices are laid down in a fixed sequence of times, and therefore whoever knows the science of the ordering of time knows the sacrifices. Astronomy is not appended to the ritual system as an interest; it is the condition on which the ritual system can be executed at all. Every later development — the siddhāntas, the eclipse computations, the trigonometry of Āryabhaṭa — descends from a calendar problem set by a fire altar.

The year as a wheel of ṛta

Before there was any technical astronomy there was the observation the whole calendar rests on, put by the Ṛgveda as a riddle.

द्वादशारं नहि तज्जराय वर्वर्ति चक्रं परि द्यामृतस्य।

dvādaśāraṁ nahi taj jarāya varvarti cakraṁ pari dyām ṛtasya

Twelve-spoked, and never wearing out — the wheel of ṛta revolves around the heavens.

— Ṛgveda 1.164.11 — first line

Twelve spokes: twelve lunar months. Not wearing out: the cycle does not degrade. And it is called the wheel of ṛta — the same word used for moral and cosmic order — which is why a calendar in this tradition is never merely administrative. The verse goes on to name 720 paired children standing in it, read since antiquity as the 360 days and 360 nights of the schematic year. That number is a convention, not an observation, and the tradition knew it: the whole subsequent history of Indian calendrics is the work of reconciling a 360-day scheme, a 354-day lunar year and a 365-day solar year, which is where the intercalary adhika māsa comes from.

The three skandhas

Skandha	Sanskrit	Subject
Siddhānta / Gaṇita	सिद्धान्त	Mathematical astronomy: planetary positions, eclipses, the length of the year, spherical calculation
Saṁhitā	संहिता	Mundane: weather, seasons, agriculture, omens, architecture, collective events
Horā	होरा	The individual: natal chart, daśā periods, praśna (enquiry), muhūrta (election of time)

The nakṣatra system

Indian time-reckoning is lunar-stellar before it is solar. The zodiac is divided into 27 nakṣatras of 13°20′ each — 28 with Abhijit — through which the moon passes in a sidereal month, one per day approximately. The nakṣatra of the moon at birth is the primary marker of temperament, and it carries the varṇa grouping described elsewhere on this site.

The pañcāṅga — five limbs of the day

Limb	What it measures
Tithi	The lunar day — the 12° separation of moon from sun; 30 in a lunar month
Vāra	The weekday, ruled by its planet
Nakṣatra	The lunar mansion the moon occupies
Yoga	The combined longitude of sun and moon, in 27 divisions
Karaṇa	Half a tithi; 11 kinds, four fixed and seven repeating

Jyotiṣa — the eye of the Veda

The year as a wheel of ṛta

The three skandhas

The nakṣatra system

The pañcāṅga — five limbs of the day

The sources of knowledge in Sanātana Dharma

Śruti — that which was heard

Smṛti — that which was remembered

Nigama and Āgama — the two revealed streams

The four Vedas

Ṛgveda