{"release":{"id":"DR1","released_on":"2026-08-21","doi":null,"url":"https://spacecatalog.org/releases#dr1"},"epoch":{"requested":"now","label":"J2026.778","julian_year":2026.778,"time":"2026-10-12T01:33:32.539Z","years_from_j2000":26.778,"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-188","name":"NGC 188","class":"open_cluster","category":"cluster","object_type":"Open cluster","mag":8.1,"mag_band":"V","abs_mag":null,"abs_mag_band":null,"distance_ly":5942.10220823158,"distance_method":"Gaia DR3 cluster membership (Hunt & Reffert 2024)","ra_deg":11.864708333333333,"dec_deg":85.26963888888889,"epoch_ra_deg":12.572213,"epoch_dec_deg":85.416675,"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":"Cepheus","discovered":"1831","featured":false,"url":"https://spacecatalog.org/object/ngc-188","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":{"b_mag":8.91,"v_mag":8.1,"redshift":-0.000139,"wikidata_id":"Q696260","also_known_as":["Polarissima Cluster"],"discovered_by":"John Frederick William Herschel","ngc_type_code":"OCl","uncertainties":{"distance_ly":[9.950507994538627,9.983945774692284]},"major_axis_arcmin":17.7,"wikipedia_article":"NGC 188","distance_reference":"NGC 188","radial_velocity_km_s":-42},"designations":[{"catalog":"Caldwell","designation":"C 1"},{"catalog":"IAU cluster","designation":"C 0039+850"},{"catalog":"MWSC","designation":"MWSC 74"},{"catalog":"NGC","designation":"NGC 188"}],"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."}