How EnteAstro calculates

Positions come from JPL DE440s — NASA's Jet Propulsion Laboratory Development Ephemeris, the same data JPL's own Horizons service is built on. It is public domain, it lives in EnteAstro's deployment as a 32.7 MB file, and it is read by enteastro-jpl 2.0.0, code written for this product.

There is no licensed astrology engine in this path and no external service is called to calculate anything. That is a deliberate commitment rather than a technical accident: it means the price of your reading does not depend on somebody else's API bill, and that EnteAstro can answer for its own arithmetic.

Reading coordinates out of an ephemeris is not the same as knowing where a planet appears. Four corrections stand in between, and all four are applied: the Earth's own position is subtracted, light travel time is solved by iteration (Jupiter is seen where it was up to fifty minutes ago), the Sun's gravity bends the light, and the Earth's orbital motion tilts every apparent direction by up to twenty arcseconds — aberration, the largest of the four. Only then is the direction rotated into the zodiac.

Checked against JPL Horizons at twelve dates from 1850 to 2149, across all ten bodies. Worst disagreement anywhere: 0.39 arcseconds. Within living memory it is under 0.05. For scale, a Pada — the finest division this product shows you — is 12,000 arcseconds wide.

What that residual is. It is not noise. It grows with distance from the year 2000, is the same for every planet, and lies entirely in one coordinate — the signature of a difference in precession model. EnteAstro uses the current IAU 2006 and IAU 2000B standards; Horizons' ecliptic output uses the older 1976 and 1980 models. Where the two differ, EnteAstro is on the newer one.

The limit worth knowing: the ephemeris is no longer the weakest link. A birth time recorded to the nearest minute carries an Ascendant uncertainty of about fifteen arcminutes — roughly two thousand times larger than anything the calculation contributes. The date range is 1850 to 2150; outside it EnteAstro says it cannot calculate rather than extrapolating.

The two zodiacs are kept entirely apart. A chart carries exactly one, every longitude in it is expressed in that one, and the ayanamsa is applied once at the boundary — never twice, and never inside a house algorithm. Kerala and Vedic surfaces are sidereal; Western is tropical.

An ayanamsa is not really an angle that grows — it is a fixed direction in space, and what moves is the vernal point. EnteAstro stores each definition as that fixed direction, calibrated to reproduce the value its own tradition published at its own reference epoch, and lets the modern IAU precession and nutation models do the rest.

The default is Lahiri, the Indian Calendar Reform Committee's official value. It is calibrated to 23°15′00.658″ at 1956 March 21.0 and reproduces the independently published J2000 value of 23.853222° to within 0.35 arcseconds. A Nakshatra is 48,000 arcseconds wide.

A birth certificate records a wall-clock time in a place; a chart needs an instant. Converting between them is the most common source of a wrong chart in astrology software, and it is wrong in a way that never looks wrong.

EnteAstro resolves against the IANA time zone database for the historical date. Somebody born in Dublin in January 1970 was on UTC+1, because Ireland kept summer time all year round from 1968 to 1971; today's January offset is UTC+0, and using it would move their Ascendant by fifteen degrees. India's wartime summer time, the 1955 unification of Bombay and Calcutta time, and pre-standard local mean times are all handled for the same reason.

Resolution happens once, at entry, and the instant is stored. Re-resolving on every read would mean a future update to the zone database silently moved an existing chart.

Where a wall-clock time is genuinely ambiguous — inside a fall-back hour that happened twice, or a spring-forward gap that never happened at all — EnteAstro says so and shows both, rather than picking one.

With no birth time there is no Ascendant, no Midheaven and no house placements, and EnteAstro produces none of them. It does not assume noon. An invented Ascendant is not a small error — it is a different chart.

What can still be calculated is calculated: the slower bodies' signs, and usually the Moon's Nakshatra. The Moon moves about thirteen degrees a day and a Nakshatra is thirteen degrees and twenty minutes wide, so if it crosses a boundary on the birth date the product names both and says the time of day decides it.

Indian charts use whole-sign houses, which is not a simplification — it is the division the Rasi chart has always used. Western charts default to Placidus, and where Placidus is genuinely undefined, inside the polar circles, the product says so and shows equal houses instead of silently substituting them.

Western aspects are angular relationships in degrees, with a stated orb: a base orb per aspect, plus two degrees when the Sun or Moon is involved, and nothing else. Applying and separating are computed from the bodies' actual daily motions.

Graha drishti is a different idea and shares no code with it. It is counted in whole signs, has no orb, and is asymmetric — Saturn aspects the third sign from itself, and what stands there does not aspect Saturn back. Every graha takes the seventh; Mars also the fourth and eighth, Jupiter the fifth and ninth, Saturn the third and tenth.

A life does not begin at the start of a Mahadasha. It begins wherever the natal Moon sits inside its Nakshatra, and the first period is only the remaining fraction of that lord's term. EnteAstro computes that balance from the Moon's actual position and shows the arithmetic.

The length of a Dasha year is genuinely contested. EnteAstro uses 365.25 days, the convention mainstream jyotisha software and most practitioners use, and also implements the classical 360-day savana year. The two diverge by about six months over a 35-year life and a full year over seventy, so the choice is recorded against every calculation rather than assumed.

A Panchang is a statement about the sky over one spot of ground. Sunrise uses the upper limb of the Sun with atmospheric refraction — the drik convention Indian Panchangs use — and Rahu Kalam, Yamagandam and Gulika are eighths of that day's actual daylight at that place, never fixed clock times.

Tithi and Karana come from the Moon's elongation from the Sun, so the ayanamsa cancels and they are the same under every sidereal system. Yoga comes from the sum of the two sidereal longitudes, where the ayanamsa does not cancel — it doubles — so Yoga is specific to the ayanamsa in force.

Engine version 1.0.0, ruleset 2.0.0. The order matters: the sky is measured first, and the interpretation is attached to what was measured. Nothing is written and then justified.

Each factor is scored from two independent parts. Significance is how much weight the tradition gives that kind of factor; distinctiveness is how much it is about today rather than about this year. Keeping them separate is what prevents the two failure modes — a reading made entirely of Saturn, which would be the same for months, or one made entirely of the Moon.

Where the running Dasha lord is also the transiting body, the factor is weighted up. That is not a tuning choice: reading a transit through the period you are actually in is the central idea of Vedic prediction, and treating the Dasha as a separate paragraph would lose it.

Every reading shows its factors, ranked, with the strength assigned to each — and says how many of them come from your own chart. If none do, it says that too, rather than presenting a Tithi shared by eight billion people as a personal reading.

No AI decides any fact in this product. Nakshatra, Rasi, Lagna, planetary positions, Dasha, Tithi, transits, aspects and numerology numbers are all deterministic calculations, and a language model touches none of them.

The interpretation corpus is a first edition, written from the classical sources and deliberately restrained. It has not yet been reviewed by a practising astrologer, and the product says so rather than implying an authority it has not earned.

EnteAstro makes no medical, mortality, fertility, criminality or mental-health claim from a chart or from a hand, in any framing. Astronomical positions are verifiable; astrological interpretation and palmistry are traditional interpretive practices and are not scientifically established methods of predicting life outcomes.

Place names, coordinates and time zones come from GeoNames, used under CC BY 4.0. Time zone rules come from the IANA database. Positional astronomy follows Meeus, Astronomical Algorithms (2nd ed.). The ayanamsa constants are the published values compiled in the Swiss Ephemeris source; no Swiss Ephemeris code is compiled, linked or distributed by this product.

The Vedic material rests on the Brihat Parashara Hora Shastra and B. V. Raman; the Kerala material on Malayalam Panchangam convention; the Western on Ptolemy and Robert Hand; numerology on Cheiro and Juno Jordan; palmistry on Benham, whose claims about health and longevity are rejected rather than repeated.