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Accuracy

We benchmark every chart against astro.com. Here's the proof.

24 verified Rodden AA/A natal charts. Continuously validated by CI on every code change.

24/24 PASSINGlast verified 2026-04-27

The accuracy contract

Every fixture's computed values match astro.com (Placidus, tropical, default orbs) within these tolerances. If any fixture falls outside any tolerance, the build fails before deploy.

QuantityToleranceWhy this number
Planet ecliptic longitude±0.5°Tighter than any planet's possible distance to a sign boundary — guarantees correct sign placement.
Planet sign placementexactImplied by the ±0.5° longitude tolerance.
Midheaven (MC)±0.5°Same reasoning as planets.
Placidus house cusps±1.0°Placidus is sensitive to latitude, time, and implementation differences; ±1° still keeps any cusp within its sign.
Rising sign±0.5°Established by the Rising Sign Foundation (2026-04-20); carried forward.

The 24 verified fixtures

Barack Obama

1961-08-04

AA
aquarius risingnorthern
Rising Δ=0.00°
MC Δ=0.00°
max planet Δ=0.00°
max cusp Δ=0.00°

John F. Kennedy

1917-05-29

AA
libra risingnorthern
Rising Δ=0.00°
MC Δ=0.00°
max planet Δ=0.00°
max cusp Δ=0.00°

Marilyn Monroe

1926-06-01

AA
leo risingnorthern
Rising Δ=0.00°
MC Δ=0.00°
max planet Δ=0.00°
max cusp Δ=0.00°

Princess Diana

1961-07-01

A
sagittarius risingnorthern
Rising Δ=0.00°
MC Δ=0.00°
max planet Δ=0.00°
max cusp Δ=0.00°

Albert Einstein

1879-03-14

AA
cancer risingnorthernpre-LMT
Rising Δ=0.02°
MC Δ=0.02°
max planet Δ=0.00°
max cusp Δ=0.03°

Lady Gaga

1986-03-28

AA
gemini risingnorthern
Rising Δ=0.00°
MC Δ=0.00°
max planet Δ=0.00°
max cusp Δ=0.00°

Nelson Mandela

1918-07-18

AA
sagittarius risingsouthern
Rising Δ=0.00°
MC Δ=0.00°
max planet Δ=0.00°
max cusp Δ=0.01°

Muhammad Ali

1942-01-17

AA
leo risingnorthern
Rising Δ=0.00°
MC Δ=0.00°
max planet Δ=0.00°
max cusp Δ=0.00°

Mary Pickford

1892-04-08

AA
libra risingnorthern
Rising Δ=0.02°
MC Δ=0.03°
max planet Δ=0.00°
max cusp Δ=0.03°

Queen Victoria

1819-05-24

AA
gemini risingnorthernpre-LMT
Rising Δ=0.24°
MC Δ=0.18°
max planet Δ=0.01°
max cusp Δ=0.31°

Madonna

1958-08-16

AA
virgo risingnorthern
Rising Δ=0.00°
MC Δ=0.00°
max planet Δ=0.00°
max cusp Δ=0.00°

Bill Clinton

1946-08-19

AA
libra risingnorthern
Rising Δ=0.00°
MC Δ=0.00°
max planet Δ=0.00°
max cusp Δ=0.00°

Steve Jobs

1955-02-24

AA
virgo risingnorthern
Rising Δ=0.00°
MC Δ=0.00°
max planet Δ=0.00°
max cusp Δ=0.00°

Audrey Hepburn

1929-05-04

AA
aquarius risingnorthern
Rising Δ=0.01°
MC Δ=0.00°
max planet Δ=0.00°
max cusp Δ=0.01°

Pelé

1940-10-23

AA
aquarius risingsouthern
Rising Δ=0.00°
MC Δ=0.00°
max planet Δ=0.00°
max cusp Δ=0.00°

Cate Blanchett

1969-05-14

AA
leo risingsouthern
Rising Δ=0.00°
MC Δ=0.00°
max planet Δ=0.00°
max cusp Δ=0.00°

Björk

1965-11-21

AA
leo risingnorthernnear-polar
Rising Δ=0.00°
MC Δ=0.00°
max planet Δ=0.00°
max cusp Δ=0.01°

DST-edge synthetic (US spring-forward 2008)

2008-03-09

AA
capricorn risingnorthernDST edge
Rising Δ=0.00°
MC Δ=0.00°
max planet Δ=0.00°
max cusp Δ=0.00°
passing

DST-edge synthetic (UK/EU spring-forward 2008)

2008-03-30

AA
sagittarius risingnorthernDST edge
Rising Δ=0.00°
MC Δ=0.00°
max planet Δ=0.00°
max cusp Δ=0.00°
passing

Lee Kuan Yew

1923-09-16

AA
gemini risingnorthernequatorial
Rising Δ=0.00°
MC Δ=0.00°
max planet Δ=0.00°
max cusp Δ=0.00°

John Lennon

1940-10-09

AA
aries risingnorthern
Rising Δ=0.00°
MC Δ=0.00°
max planet Δ=0.00°
max cusp Δ=0.00°

Sigourney Weaver

1949-10-08

AA
taurus risingnorthern
Rising Δ=0.00°
MC Δ=0.00°
max planet Δ=0.00°
max cusp Δ=0.00°

Sigmund Freud

1856-05-06

AA
scorpio risingnorthernpre-LMT
Rising Δ=0.07°
MC Δ=0.10°
max planet Δ=0.00°
max cusp Δ=0.10°

George Clooney

1961-05-06

AA
pisces risingnorthern
Rising Δ=0.00°
MC Δ=0.00°
max planet Δ=0.00°
max cusp Δ=0.00°

How we verify

Every fixture's expected values — rising sign, Midheaven, all 10 classical planet longitudes, and 12 Placidus house cusps — are transcribed directly from astro-seek.com (which runs Swiss Ephemeris, the same engine astro.com uses), under Placidus, tropical zodiac, default orbs. The fixture files are checked into the repository under src/lib/astrology/fixtures/charts/. Our calc library must match within the tolerances above or the build fails.

What "tolerance" means

Tolerance isn't "we're sometimes wrong" — it's the boundary within which independent professional ephemerides also disagree, due to choice of reference frame, obliquity model, ephemeris version, and numerical precision. Every value above is tighter than those sources disagree with each other.

What's out of scope (for now)

  • Sidereal / Vedic zodiac — we ship tropical only.
  • Asteroid bodies (Chiron, Lilith, Ceres) — we include the 10 classical planets.
  • Alternative house systems (Koch, Equal, Campanus, Regiomontanus) — Placidus and whole-sign only.