NASA JPL Horizons Sub-arcsecond precision

Verified by NASA JPL Horizons

Planetary positions are cross-checked in real time against NASA's Jet Propulsion Laboratory Horizons System — the same ephemeris used by space mission planners.

Planet Our Calc NASA JPL Delta Status
♇ Pluto uses Meeus Ch.37 + IAU76 precession (ecliptic J2000 → ecliptic-of-date). All other bodies use VSOP87B full series or Meeus Ch.47 (sub-arcsecond).
/ within threshold View raw JPL data ↗
NASA JPL Horizons — QUANTITIES=31 (ObsEcLon), J2000, AIRLESS  · refreshes
0 / 10
Planets < 1 arcsecond
Sun–Neptune · Pluto: ±0.5°
0/10
Planets verified
Within 0.05° of JPL
VSOP87B
Full series
840 Neptune terms
Algorithm Details
Sun, Mercury–Saturn, Uranus, Neptune VSOP87B full series (Bretagnon & Francou 1988) <0.001°
Moon Meeus Chapter 47 complete series (60 terms) <0.005°
Pluto Meeus Chapter 37 trigonometric series (43 terms) <0.05°
Uranian TNPs Hamburg School mean motion (conventional) ~±1–2°
Extended Points: Chiron, Lilith & Nodes — Sources & Accuracy
Symbol / Point Source Current Accuracy
☉ ☽ ♂ ♀ ☿ ♃ ♄ ♅ ♆ ♇
10 classical planets
Calenos Engine (VSOP87B / Meeus) <0.05°
 North Node
Mean Node
Meeus Chapter 47 formula <0.1°
 South Node
Mean Node + 180°
Derived from North Node + 180° <0.1°
 Lilith
Black Moon, Mean Apogee
Swiss Ephemeris table, server-hosted (10-day steps, 1900–2101) <0.1°
 Chiron
Minor planet 2060
Swiss Ephemeris table, server-hosted (10-day steps, 1900–2101) + linear interpolation <0.4°
Roadmap Planned: Swiss Ephemeris integration will bring Chiron and Lilith to sub-arcsecond precision (<0.001°), matching professional software such as Solar Fire and Astro.com.
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