{"release":{"id":"DR1","released_on":"2026-08-21","doi":null,"url":"https://spacecatalog.org/releases#dr1"},"epoch":{"requested":"now","label":"J2026.668","julian_year":2026.668,"time":"2026-09-02T01:47:02.396Z","years_from_j2000":26.668,"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-4253","name":"NGC 4253","class":"barred_spiral_galaxy_sba","category":"galaxy","object_type":"Barred spiral galaxy SBa","mag":13.23,"mag_band":"V","abs_mag":null,"abs_mag_band":null,"distance_ly":192870106.75956342,"distance_method":"redshift (CMB frame), flat ΛCDM with H0 = 70 km/s/Mpc","ra_deg":184.61045833333336,"dec_deg":29.81286111111111,"epoch_ra_deg":184.948657,"epoch_dec_deg":29.663721,"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":"Coma Berenices","discovered":"1788","featured":false,"url":"https://spacecatalog.org/object/ngc-4253","radius_km":null,"radius_kind":null,"data_quality":null,"description":null,"properties":{"b_mag":13.72,"h_mag":10.38,"j_mag":11.1,"k_mag":9.84,"v_mag":13.23,"redshift":0.01271,"hubble_type":"SBa","wikidata_id":"Q1110198","redshift_cmb":0.0136656733477587,"discovered_by":"William Herschel","ngc_type_code":"G","uncertainties":{"distance_ly":[16119475.787472151,16119475.787472151]},"major_axis_arcmin":0.89,"minor_axis_arcmin":0.64,"wikipedia_article":"NGC 4253","position_angle_deg":73,"surface_brightness":22.05,"radial_velocity_km_s":3786},"designations":[{"catalog":"2MASX","designation":"2MASX J12182648+2948461"},{"catalog":"IRAS","designation":"IRAS 12159+3005"},{"catalog":"IRAS","designation":"IRAS F12159+3005"},{"catalog":"LEDA","designation":"LEDA 39525"},{"catalog":"MCG","designation":"MCG +05-29-051"},{"catalog":"NGC","designation":"NGC 4253"},{"catalog":"PGC","designation":"PGC 39525"},{"catalog":"SDSS","designation":"SDSS J121826.51+294846.5"},{"catalog":"UGC","designation":"UGC 7344"}],"source":{"id":"openngc","name":"OpenNGC","url":"https://github.com/mattiaverga/OpenNGC","license":"CC-BY-SA-4.0"},"updated_at":"2026-09-01T22:58:55.274Z","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."}