{"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":"2026-09-06T15:02:25.773Z","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-3661","name":"NGC 3661","class":"lenticular_galaxy_s0_a","category":"galaxy","object_type":"Lenticular galaxy S0-a","mag":14.34,"mag_band":"B","abs_mag":null,"abs_mag_band":null,"distance_ly":335188150.7370071,"distance_method":"redshift (CMB frame), flat ΛCDM with H0 = 70 km/s/Mpc","ra_deg":170.910125,"dec_deg":-13.831111111111111,"epoch_ra_deg":171.248035,"epoch_dec_deg":-13.978507,"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":"Crater","discovered":"1786","featured":false,"url":"https://spacecatalog.org/object/ngc-3661","radius_km":null,"radius_kind":null,"data_quality":null,"description":null,"properties":{"b_mag":14.34,"h_mag":10.1,"j_mag":10.82,"k_mag":9.84,"redshift":0.022325,"hubble_type":"S0-a","wikidata_id":"Q1105777","redshift_cmb":0.02357539659818575,"discovered_by":"William Herschel","ngc_type_code":"G","uncertainties":{"distance_ly":[19615356.37209574,19615356.37209574]},"major_axis_arcmin":1.77,"minor_axis_arcmin":0.75,"position_angle_deg":139,"surface_brightness":24.08,"radial_velocity_km_s":6618},"designations":[{"catalog":"2MASX","designation":"2MASX J11233844-1349520"},{"catalog":"IC","designation":"IC 689"},{"catalog":"IRAS","designation":"IRAS F11211-1333"},{"catalog":"LEDA","designation":"LEDA 34986"},{"catalog":"MCG","designation":"MCG -02-29-022"},{"catalog":"NGC","designation":"NGC 3661"},{"catalog":"PGC","designation":"PGC 34986"}],"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."}