Most astrology apps interpret. We calculate. That’s not a marketing line — it’s a technical decision with real consequences for accuracy, consistency, and respect for the tradition.
The distinction matters more than it sounds.
When an app “interprets,” it applies a layer of editorial judgment between the planetary positions and the output you see. Someone decided what Ketu in the 7th house “means.” Someone decided how to weight the dasha period against the transit. That someone may have been a competent astrologer — or they may have been a developer trying to ship a feature. Either way, you’re getting their interpretation wrapped in automation.
When we calculate, we compute positions. We apply rules from classical texts. We output what the math produces. Interpretation, when it happens, is something a trained practitioner does from those numbers — not something baked invisibly into an algorithm.
The Engine Under Everything
The planetary positions in Jyotiṣ come from Swiss Ephemeris — the same computational engine used by the Jet Propulsion Laboratory for space mission planning. It provides sub-arcsecond accuracy going back 13,000 years and forward several thousand more. For an astrology application, this is not overkill. Longitude precision matters when you’re calculating nakṣatra pāda, when a planet sits near a rāśi boundary, when the exact moment of a transit determines the quality of a muhūrta.
Using a lower-accuracy source for planetary positions is like using a ruler graduated in centimeters to measure for surgery. The imprecision compounds. A degree of error in Jupiter’s longitude propagates into wrong nakṣatra assignments, wrong dasha calculations, wrong divisional charts. Swiss Ephemeris eliminates this category of error. Everything else builds on that foundation.
Where the Tropical System Goes Wrong
The Lahiri ayanamṣa is the difference between pointing at the map and pointing at the territory.
The tropical zodiac — the system used in Western astrology — was calibrated around 100–200 CE when the vernal equinox coincided with the beginning of Aries. That alignment no longer exists. Due to the precession of the equinoxes, the sky has shifted roughly 24° since that calibration. When a Western astrologer today says “the Sun is in Aries,” the Sun is actually in Pisces — by the stars, by actual sky position, by observable reality.
Jyotiṣa is sidereal. It measures planets against the fixed stars, not against a reference point that has drifted away from the stars over two millennia. The Lahiri ayanamṣa — the most widely used among Indian schools and the one officially adopted by the Indian government’s calendar reform — is the adjustment applied to the tropical longitude to produce the sidereal position.
The BPHS (Bṛhat Parāśara Horā Śāstra, Chapter 4) describes the nakṣatras in terms of fixed stellar positions. There is no ambiguity: the tradition is sidereal, and using a tropical zodiac for Jyotiṣa calculations produces results that are internally inconsistent with the classical source texts.
The House System Parāśara Taught
Whole-sign houses are not a preference. They are what the tradition specifies.
The Bṛhat Parāśara Horā Śāstra, throughout its treatment of bhāvas, defines the first house as the entire sign of the lagna — not a slice of it, not an arc computed by quadrant division, but the whole rāśi. The second house is the next complete rāśi, and so on through all twelve. This is the system Parāśara describes. It is also the system found in Praśna Mārga, in Sārāvalī, in Phaladeepika — the classical corpus is remarkably consistent on this point.
Placidus, Koch, Equal House, Porphyry — these are later inventions, most of them developed within Western astrology to solve a problem that doesn’t exist in the whole-sign framework. Some of them fail to produce houses at all at extreme latitudes above 66°. Whole-sign houses work everywhere, because a rāśi is a rāśi regardless of geography.
The reason modern software defaults to Placidus is not that it’s more accurate. It’s that Western astrological software was written first, and its defaults became the template. We don’t use that template. We use what the texts actually prescribe.
On Hybridization
There is a tendency — particularly in English-language astrology publishing — to combine Jyotiṣa and Western astrology. A Vedic practitioner adds Chiron. A Western practitioner adopts dashas. The result is presented as synthesis or evolution.
It is neither. It is confusion.
Jyotiṣa and Western astrology are complete, internally coherent systems built on different metaphysical foundations. Jyotiṣa operates with sidereal longitudes, a specific set of grahas, a complex dignity system based on the 16 varga charts, dasha systems rooted in nakṣatra position, and a philosophical framework drawn from the Vedic tradition. Western astrology operates with tropical longitudes, a different set of significators, modern outer planets, and psychological interpretive frameworks developed in the 20th century.
When you add Western elements to a Jyotiṣa reading, you’re not enriching the system — you’re undermining the internal logic of both. A Jyotiṣa chart has no technical framework for Chiron. A Western chart has no sidereal framework for nakṣatra-based dashas. Mixing them produces answers that can’t be tested, verified, or traced back to a primary source. It produces vibes dressed as scholarship.
We don’t hybridize. If a question requires classical Jyotiṣa, we answer with classical Jyotiṣa.
When We Don’t Know, We Say So
Praśna Mārga — the principal classical text on horary Jyotiṣa — is specific when it has rules to give and silent when it doesn’t. That silence is intentional. The tradition drew a line between what can be calculated and what cannot.
The software follows the same discipline. When a classical rule applies, we apply it. When the texts disagree, we note the disagreement. When there is no clear rule for a given situation, we do not invent one. The output is smaller as a result — but it’s accurate.
This is unusual in an industry built on confident vagueness. Most horoscope systems produce an answer for every question because uncertainty is commercially unpopular. We produce an answer when the texts support one, and we indicate uncertainty when they don’t.
The Pañchāṅga Is Not a Horoscope
The Pañchāṅga — the traditional Hindu almanac — is five calculated quantities: Vāra (day of week), Tithi (lunar phase), Nakṣatra (lunar mansion), Yoga (a function of combined solar and lunar longitudes), and Karaṇa (half-tithi). These are not horoscope elements. They are astronomical measurements.
A tithi is a precise arc — 12° of separation between the Sun and Moon. A nakṣatra pāda is a 3°20’ arc of the ecliptic. A yoga is a specific computed value. These quantities are either correct or they are not — there is no room for interpretation in their derivation, only in their application.
When Jyotiṣ displays the Pañchāṅga, it displays five numbers computed from Swiss Ephemeris. Not five impressions. Not five suggestions. Numbers.
Precision is not cold. It is respectful — of the mathematics that underlies this tradition, of the practitioners who built it over centuries, and of the person who comes with a genuine question and deserves a genuine answer.
The tools we use exist to protect that respect.