Two named ephemeris paths. One transparent decision.
The documented API exposes Formula-Lite and JPL DE440 as explicit provider choices. Select the one that meets the date range, precision and distribution requirements of your own product.
Know the method behind the answer.
| Question | Formula-Lite | JPL DE440 |
|---|---|---|
| Documented provider | tkr_formula | de440 |
| Astronomical basis | In-house VSOP87-series implementation using public coefficients. | In-house reader for NASA JPL's DE440 kernel. |
| Distribution characteristic | Series arithmetic; no DE440 kernel file is required for this provider. | Requires the relevant ephemeris kernel in its deployment model. |
| Evaluation question | Does its tested precision and range satisfy your product? | Does its kernel size and operational model fit your product? |
Reproducible output starts with recorded inputs.
A silent switch in ephemeris, ayanamsa or location handling can create chart differences that are hard to explain. The documented platform requires the provider to be named, and returns its identity with the calculation.
- Test edge dates: validate both the beginning and end of your required range.
- Record conventions: ayanamsa and regional settings belong alongside results.
- Compare references: verify representative cases rather than relying on marketing adjectives.
{
"provider": "tkr_formula"
}
or
{
"provider": "de440"
}Ephemeris questions
Is VSOP87 the same as Swiss Ephemeris?
No. Formula-Lite is described as an in-house VSOP87-series implementation. That is a different claim from licensing or bundling Swiss Ephemeris.
Does this site offer DE441?
No. DE441 is not presented here as a released product or provider. Ask for written status if a future ephemeris is part of your requirements.
Can both providers run offline on mobile?
Do not assume that. Local distribution of a kernel and a compact series-based runtime have different requirements; obtain a platform-specific licence and build evaluation.
Choose by evidence, not by label.
Bring your dates, locations, reference cases and deployment constraints.