{"release":{"id":"DR1","released_on":"2026-08-21","doi":null,"url":"https://spacecatalog.org/releases#dr1"},"epoch":{"requested":"now","label":"J2026.807","julian_year":2026.807,"time":"2026-10-22T21:36:27.724Z","years_from_j2000":26.807,"frame":"date","applied":"Proper motion, then precession and nutation. The catalogued position is carried along the great circle the object's own published motion puts it on, at a constant velocity, from the epoch that position was measured at, 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. The motion runs from position_epoch_jyear where the upstream publishes one — a timed pulsar's position belongs to the year it was timed — and from J2000 where it does not. 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-6520","name":"NGC 6520","class":"open_cluster","category":"cluster","object_type":"Open cluster","mag":7.6,"mag_band":"V","abs_mag":null,"abs_mag_band":null,"distance_ly":5570.807684894795,"distance_method":"Gaia DR3 cluster membership (Hunt & Reffert 2024)","ra_deg":270.85058333333336,"dec_deg":-27.88611111111111,"epoch_ra_deg":271.275551,"epoch_dec_deg":-27.885547,"epoch_moved_arcsec":null,"pm_ra_mas_yr":null,"pm_dec_mas_yr":null,"position_epoch_jyear":null,"orbits":null,"semi_major_axis_km":null,"periapsis_km":null,"mass_kg":null,"mass_msun":null,"constellation":"Sagittarius","discovered":"1784","featured":false,"url":"https://spacecatalog.org/object/ngc-6520","source":{"id":"openngc","name":"OpenNGC","url":"https://github.com/mattiaverga/OpenNGC","license":"CC-BY-SA-4.0","attribution":"OpenNGC, Mattia Verga (github.com/mattiaverga/OpenNGC). Fields derived from it stay under CC BY-SA 4.0.","commercial_use":"allowed"},"radius_km":null,"radius_kind":null,"data_quality":null,"description":null,"properties":{"v_mag":7.6,"redshift":-0.000092,"wikidata_id":"Q1368288","discovered_by":"William Herschel","ngc_type_code":"OCl","uncertainties":{"distance_ly":[18.29639288568836,18.417370450538478]},"major_axis_arcmin":5.4,"wikipedia_article":"NGC 6520","distance_reference":"NGC 6520","radial_velocity_km_s":-28},"designations":[{"catalog":"ESO","designation":"ESO 456-SC42"},{"catalog":"IAU cluster","designation":"C 1800-279"},{"catalog":"MWSC","designation":"MWSC 2790"},{"catalog":"NGC","designation":"NGC 6520"}],"updated_at":"2026-10-01T09:42:28.932Z","attribution":"Data from SpaceCatalog.org. Each record names its upstream in `source`, with that producer's terms in `source.license`, the acknowledgement it asks for in `source.attribution`, and whether its terms allow commercial use in `source.commercial_use`; those terms govern the record, and citing SpaceCatalog does not discharge them."}