{"release":{"id":"DR1","released_on":"2026-08-21","doi":null,"url":"https://spacecatalog.org/releases#dr1"},"epoch":{"requested":"now","label":"J2026.667","julian_year":2026.667,"time":"2026-09-01T15:53:06.741Z","years_from_j2000":26.667,"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":"ic-2391","name":"ο Vel Cluster","class":"open_cluster","category":"cluster","object_type":"Open cluster","mag":2.5,"mag_band":"V","abs_mag":null,"abs_mag_band":null,"distance_ly":493.4745994854328,"distance_method":"Gaia DR2 cluster membership (Cantat-Gaudin+ 2020)","ra_deg":130.13283333333334,"dec_deg":-53.03547222222222,"epoch_ra_deg":130.322943,"epoch_dec_deg":-53.130233,"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":"Vela","discovered":"1751","featured":false,"url":"https://spacecatalog.org/object/ic-2391","radius_km":null,"radius_kind":null,"data_quality":null,"description":null,"properties":{"v_mag":2.5,"redshift":0.000049,"wikidata_id":"Q915499","discovered_by":"Nicolas Louis de Lacaille","ngc_type_code":"OCl","major_axis_arcmin":29.1,"wikipedia_article":"IC 2391","distance_reference":"IC 2391","radial_velocity_km_s":15},"designations":[{"catalog":"Caldwell","designation":"C 85"},{"catalog":"Common name","designation":"omi Vel Cluster"},{"catalog":"IAU cluster","designation":"C 0838-528"},{"catalog":"IC","designation":"IC 2391"},{"catalog":"MWSC","designation":"MWSC 1529"}],"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."}