{"release":{"id":"DR1","released_on":"2026-08-21","doi":null,"url":"https://spacecatalog.org/releases#dr1"},"epoch":{"requested":"now","label":"J2026.680","julian_year":2026.68,"time":"2026-09-06T05:40:14.100Z","years_from_j2000":26.68,"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-6888","name":"Crescent Nebula","class":"h_ii_region","category":"nebula","object_type":"H II region","mag":7.44,"mag_band":"B","abs_mag":null,"abs_mag_band":null,"distance_ly":null,"distance_method":null,"ra_deg":303.02729166666666,"dec_deg":38.35494444444445,"epoch_ra_deg":303.271268,"epoch_dec_deg":38.434805,"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":"Cygnus","discovered":"1792","featured":false,"url":"https://spacecatalog.org/object/ngc-6888","radius_km":null,"radius_kind":null,"data_quality":null,"description":null,"properties":{"b_mag":7.44,"wikidata_id":"Q202993","discovered_by":"William Herschel","ngc_type_code":"HII","major_axis_arcmin":20,"minor_axis_arcmin":10,"wikipedia_article":"Crescent Nebula"},"designations":[{"catalog":"BD","designation":"BD +37 3821"},{"catalog":"Caldwell","designation":"C 27"},{"catalog":"Common name","designation":"Crescent Nebula"},{"catalog":"HD","designation":"HD 192163"},{"catalog":"HIP","designation":"HIP 99546"},{"catalog":"LBN","designation":"LBN 203"},{"catalog":"Lynds","designation":"LBN 075.51+02.29"},{"catalog":"NGC","designation":"NGC 6888"}],"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."}