{"release":{"id":"DR1","released_on":"2026-08-21","doi":null,"url":"https://spacecatalog.org/releases#dr1"},"epoch":{"requested":"now","label":"J2026.665","julian_year":2026.665,"time":"2026-08-31T17:00:25.886Z","years_from_j2000":26.665,"frame":"date","applied":"Proper motion, then precession and nutation. The catalogued J2000 position is carried along the great circle the object's own published motion puts it on, at a constant velocity, and the result is referred to the true equator and equinox of this instant. Those are separate things: the motion moves the object, and the rotation turns the grid under it by about fifty arcseconds a year, with nutation adding up to another seventeen.","excluded":"Parallax, the radial-velocity perspective term, aberration and refraction; each is below the accuracy of the catalogued positions themselves. An object with no published proper motion comes back where the catalogue has it rather than at a fabricated zero, and says so with a null pm_ra_mas_yr. A body with no fixed position is not propagated at all — its place comes from an ephemeris, which is what /api/v1/visible answers with."},"slug":"ngc-643","name":"NGC 643","class":"open_cluster","category":"cluster","object_type":"Open cluster","mag":null,"mag_band":null,"abs_mag":null,"abs_mag_band":null,"distance_ly":null,"distance_method":null,"ra_deg":23.755958333333336,"dec_deg":-75.5568611111111,"epoch_ra_deg":23.874985,"epoch_dec_deg":-75.419193,"epoch_moved_arcsec":null,"pm_ra_mas_yr":null,"pm_dec_mas_yr":null,"orbits":null,"semi_major_axis_km":null,"periapsis_km":null,"mass_kg":null,"mass_msun":null,"constellation":"Hydrus","discovered":"1835","featured":false,"url":"https://spacecatalog.org/object/ngc-643","radius_km":null,"radius_kind":null,"data_quality":null,"description":null,"properties":{"h_mag":12.29,"j_mag":12.97,"k_mag":11.99,"wikidata_id":"Q1037861","discovered_by":"John Frederick William Herschel","ngc_type_code":"OCl","major_axis_arcmin":2.2,"minor_axis_arcmin":2.2,"wikipedia_article":"NGC 643"},"designations":[{"catalog":"2MASX","designation":"2MASX J01350142-7533250"},{"catalog":"ESO","designation":"ESO 029-050"},{"catalog":"ESO","designation":"ESO 29-50"},{"catalog":"NGC","designation":"NGC 643"}],"source":{"id":"openngc","name":"OpenNGC","url":"https://github.com/mattiaverga/OpenNGC","license":"CC-BY-SA-4.0"},"updated_at":"2026-08-30T09:56:50.739Z","attribution":"Data from SpaceCatalog.org. Individual records carry their source and license in `source`; attribution is required for CC-BY and CC-BY-SA rows."}