Bodies and the ecliptic
What RAINBOW actually measures when it samples the sky. · 8 min
What is being measured
RAINBOW’s astronomy layer records geocentric ecliptic longitude and latitude of date, plus J2000 RA/Dec, distance, and a finite-difference longitude velocity. It does not store a “sign meaning”.
Sky at 2020-12-21 18:20 UTC · geocentric, true ecliptic of date. No market claim.
Key points
- The ecliptic is the Earth’s orbital plane projected on the sky. Longitude 0° is the true equinox of date.
- Bodies in the Lab are identity metadata only (name, symbol, colour, orbital group). Interpretation plugins live elsewhere.
- Accuracy is documented at about ±1′ for 1700–2200 (astronomy-engine / VSOP87, Brown/ILE Moon, DE405-calibrated Pluto).
- Geocentric positions include light-time and aberration; heliocentric positions are true positions.
Caveat
Tropical versus sidereal zodiac is an interpretation choice. It is not part of the truth layer. RAINBOW never invents Thai, Vedic or Chinese rules; those plugins declare unimplemented topics instead.
References
- astronomy-engine
- Explanatory Supplement to the Astronomical Almanac — Urban S.E. and Seidelmann P.K. (eds.), 3rd ed., University Science Books, 2013