Reference systems · ChronOS guide
Sidereal astrology API with named ayanamsha models
Sidereal astrology expresses zodiac longitude relative to a sidereal reference. The difference from tropical longitude is commonly represented by an ayanamsha, but named ayanamshas are distinct date-aware models and should not be reduced to an unlabeled fixed number.
01 / Method
Make the sidereal reference reproducible
A sidereal result should identify the ayanamsha name, model version and epoch-dependent offset. If a fixed custom offset is supported, it must be distinguishable from a named historical or institutional model.
ChronOS keeps named ayanamsha and explicit offset inputs mutually exclusive where the contract requires one reference choice. This prevents a response from appearing more historically specific than its inputs justify.
- Tropical source longitude
- Named, date-aware ayanamsha
- Ayanamsha model version
- Reference longitude and offset provenance
02 / API example
Calculate a named sidereal lunar sector
The lunar-sector endpoint requires the sector system and makes its reference choice explicit.
curl --request POST \
--url https://api.chronos-ephemeris.com/v2/lunar-sectors/calculate \
--header "Authorization: Bearer $CHRONOS_API_KEY" \
--header "Content-Type: application/json" \
--data '{
"datetime_utc": "2026-07-16T12:00:00Z",
"system": "nakshatra_27",
"ayanamsha": "lahiri"
}'Keep API keys in server-side secret storage. The example uses an environment variable and contains no production credential.
03 / Evidence
Comparing sidereal results
Two engines can both be internally consistent and still differ because they implement different ayanamsha definitions, precession transport or epoch conventions. Comparisons must pin the named model and date before evaluating the numerical difference.
ChronOS publishes the reference name and model version with supported sidereal outputs and documents convention boundaries in the capability registry.
04 / Applications
Sidereal calculation applications
The sidereal coordinate layer supports multiple astrology traditions while keeping the underlying tropical astronomical state available for audit.
- Sidereal natal and transit charts
- Nakshatra calculations
- Ingress and timeline searches
- Tradition-specific educational tools
05 / FAQ
Frequently asked questions
Does ChronOS support Lahiri ayanamsha?+
The current capability registry is the authoritative list of enabled named ayanamshas, including their identifiers and release status.
Can I provide a custom sidereal offset?+
Supported contracts distinguish a named date-aware ayanamsha from an explicit reference offset and prevent both from being applied ambiguously.
Is sidereal longitude more astronomical than tropical longitude?+
They are different reference conventions used by applications. The astronomical body state and the zodiac reference transformation should be identified separately.