About Your Sky Atlas
Your Sky Atlas calculates Western tropical birth charts and compares two charts using the same local calculation service. Interpretations are original symbolic readings for reflection, not scientific assessments or predictions.
Calculation Method
Swiss Ephemeris 2.10.03 runs on the server through @kuntay/swisseph 0.2.2. Local Swiss .se1 files supply geocentric, apparent ecliptic positions. The app refuses a reduced-precision ephemeris fallback. Supported Gregorian years are 1800–2399, subject to the converted UTC time falling inside the bundled interval.
Placidus is the default house system; Whole Sign and Equal are available. Placidus may be undefined at polar latitudes. The app reports this explicitly and asks you to select another system; it never silently substitutes one. House membership follows the exact cusps without an early-entry convention.
Black Moon Lilith uses the mean lunar apogee, not asteroid Lilith or the osculating apogee. North Node defaults to True Node with Mean Node available. The South Node is exactly opposite the selected North Node. Swiss Ephemeris documentation describes these methods.
Time Zones and Unknown Times
Local times use IANA time zones and Temporal. Ambiguous clock-back times require an explicit offset choice. Nonexistent clock-forward times and skipped dates are rejected. UTC is used as UT; DUT1 is not separately modeled.
Unknown-time placements are checked across the actual local date, including shorter or longer daylight-saving days. Signs crossing a boundary are listed as possibilities; degrees, houses, and angles are omitted from definite results. Wheels use a clearly labeled local-noon reference. Samples at most 15 minutes apart and refined detected stations bound the daily longitude range; positions extremely close to a boundary still need a recorded time.
Compatibility compares both people’s planets and known angles. Independent daily longitude ranges determine possible orb ranges when either time is unknown. Houses are not overlaid in the comparison wheel. Planetary connections are limited visually to the closest 24 eligible aspects; the table contains the full selected list.
Historical and Other Limitations
Before 1970, civil-time records may be incomplete. Before 1900, an IANA zone’s earliest local mean time can represent its reference city rather than the actual birthplace; this app does not reconstruct birthplace-specific local mean time. Future time-zone rules can change. Verify uncertain historical offsets independently before relying on houses or angles. Exact poles are excluded.
The local place search uses attributed GeoNames city data. A city center is an approximation; reliable coordinates and IANA identifiers can be entered in Advanced settings. There are no transit, composite, return, or sidereal tools in this phase.
Source & License
Your Sky Atlas is offered under AGPL-3.0-or-later, following the approved open-source licensing route. The complete source archive includes this app, build instructions, the place dataset, license notices, and the corresponding Swiss Ephemeris WASM wrapper and C source archive.
Swiss Ephemeris © Astrodienst AG; WASM wrapper © Kuntay Erkus. Place data © GeoNames, CC BY 4.0. See LICENSE and NOTICE.md inside the archive for full attribution and terms. GeoNames · CC BY 4.0