{"release":{"id":"DR1","released_on":"2026-08-21","doi":null,"url":"https://spacecatalog.org/releases#dr1"},"epoch":{"requested":"now","label":"J2026.654","julian_year":2026.654,"time":"2026-08-27T17:06:01.065Z","years_from_j2000":26.654,"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-1981","name":"Upper Sword","class":"nebula_with_cluster","category":"nebula","object_type":"Nebula with cluster","mag":4.2,"mag_band":"V","abs_mag":null,"abs_mag_band":null,"distance_ly":null,"distance_method":null,"ra_deg":83.78995833333333,"dec_deg":-4.425055555555556,"epoch_ra_deg":84.122443,"epoch_dec_deg":-4.407022,"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":"Orion","discovered":"1827","featured":false,"url":"https://spacecatalog.org/object/ngc-1981","radius_km":null,"radius_kind":null,"data_quality":null,"description":null,"properties":{"v_mag":4.2,"redshift":0.000093,"wikidata_id":"Q1046317","discovered_by":"John Frederick William Herschel","ngc_type_code":"Cl+N","major_axis_arcmin":9,"wikipedia_article":"NGC 1981","radial_velocity_km_s":28},"designations":[{"catalog":"Common name","designation":"Upper Sword"},{"catalog":"IAU cluster","designation":"C 0532-044"},{"catalog":"MWSC","designation":"MWSC 579"},{"catalog":"NGC","designation":"NGC 1981"}],"source":{"id":"openngc","name":"OpenNGC","url":"https://github.com/mattiaverga/OpenNGC","license":"CC-BY-SA-4.0"},"updated_at":"2026-08-27T16:03:54.983Z","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."}