swiss-ptolemaic-fixed-stars-1.0.0 submits the saved chart’s Julian day UT to Swiss Ephemeris fixstar2_ut using the bundled official sefstars.txt catalog. The response preserves geocentric tropical ecliptic longitude and latitude, visual magnitude, engine version, Swiss version, and the exact rules version.
Named catalog policy
The governed subset contains Aldebaran, Castor, Pollux, Regulus, Vindemiatrix, Spica, Antares, Arcturus, Vega, Fomalhaut, Betelgeuse, Rigel, Sirius, Procyon, and Canopus. Every row maps to a named star or precise bright-star locator in Ptolemy Book I chapter 9. This is a disclosed reference subset, not a claim to include every star in Ptolemy’s constellational catalog.
Distance contract
- Normalize both tropical longitudes into the 360-degree circle.
- Measure the absolute shortest circular separation.
- Compare each star with seven planets, Ascendant, and Midheaven.
- Sort the ledger by nearest distance, then star name.
- Label under one degree, one through three degrees, or beyond three degrees as descriptive inspection bands only.
Validation and provenance
Regression fixtures require all fifteen stars, verify Regulus near 29 degrees 50 minutes Leo at J2000, and prove that Spica’s tropical longitude changes by more than four and a half degrees between the 1600 and 2000 epochs. Web fixtures verify circular distance across zero Aries and deterministic nearest-point selection.