{"release":{"id":"DR1","released_on":"2026-08-21","doi":null,"url":"https://spacecatalog.org/releases#dr1"},"epoch":{"requested":"now","label":"J2026.681","julian_year":2026.681,"time":"2026-09-06T21:52:25.570Z","years_from_j2000":26.681,"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-3923","name":"NGC 3923","class":"elliptical_galaxy_e","category":"galaxy","object_type":"Elliptical galaxy E","mag":9.6,"mag_band":"V","abs_mag":null,"abs_mag_band":null,"distance_ly":96926676.00464234,"distance_method":"redshift (CMB frame), flat ΛCDM with H0 = 70 km/s/Mpc","ra_deg":177.75704166666665,"dec_deg":-28.80602777777778,"epoch_ra_deg":178.097019,"epoch_dec_deg":-28.955414,"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":"Hydra","discovered":"1791","featured":false,"url":"https://spacecatalog.org/object/ngc-3923","radius_km":null,"radius_kind":null,"data_quality":null,"description":null,"properties":{"b_mag":10.76,"h_mag":6.76,"j_mag":7.42,"k_mag":6.5,"v_mag":9.6,"redshift":0.005767,"hubble_type":"E","wikidata_id":"Q269287","redshift_cmb":0.006902679485948804,"discovered_by":"William Herschel","ngc_type_code":"G","uncertainties":{"distance_ly":[14584065.476009611,14584065.476009611]},"major_axis_arcmin":6.89,"minor_axis_arcmin":4.55,"wikipedia_article":"NGC 3923","position_angle_deg":48,"surface_brightness":23.8,"radial_velocity_km_s":1724},"designations":[{"catalog":"2MASX","designation":"2MASX J11510178-2848223"},{"catalog":"ESO","designation":"ESO 440-017"},{"catalog":"ESO","designation":"ESO 440-17"},{"catalog":"ESO-LV","designation":"ESO-LV 440-0170"},{"catalog":"LEDA","designation":"LEDA 37061"},{"catalog":"MCG","designation":"MCG -05-28-012"},{"catalog":"NGC","designation":"NGC 3923"},{"catalog":"PGC","designation":"PGC 37061"}],"source":{"id":"openngc","name":"OpenNGC","url":"https://github.com/mattiaverga/OpenNGC","license":"CC-BY-SA-4.0"},"updated_at":"2026-09-02T19:50:56.720Z","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."}