{"release":{"id":"DR1","released_on":"2026-08-21","doi":null,"url":"https://spacecatalog.org/releases#dr1"},"epoch":{"requested":"now","label":"J2026.808","julian_year":2026.808,"time":"2026-10-23T07:08:52.093Z","years_from_j2000":26.808,"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":"ic-4902","name":"IC 4902","class":"spiral_galaxy_sbc","category":"galaxy","object_type":"Spiral galaxy Sbc","mag":16.08,"mag_band":"B","abs_mag":null,"abs_mag_band":null,"distance_ly":803421446.713786,"distance_method":"redshift (CMB frame), flat ΛCDM with H0 = 70 km/s/Mpc","ra_deg":298.60045833333334,"dec_deg":-56.379083333333334,"epoch_ra_deg":299.145043,"epoch_dec_deg":-56.308535,"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":"Telescopium","discovered":null,"featured":false,"url":"https://spacecatalog.org/object/ic-4902","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":16.08,"h_mag":12.45,"j_mag":13.04,"k_mag":12.2,"redshift":0.05557,"hubble_type":"Sbc","wikidata_id":"Q3681602","redshift_cmb":0.05523478445607766,"ngc_type_code":"G","uncertainties":{"distance_ly":[35488744.010670304,35488744.010670304]},"major_axis_arcmin":0.68,"minor_axis_arcmin":0.34,"position_angle_deg":18,"surface_brightness":23.44,"radial_velocity_km_s":16197},"designations":[{"catalog":"2MASX","designation":"2MASX J19542410-5622447"},{"catalog":"ESO","designation":"ESO 185-024"},{"catalog":"ESO","designation":"ESO 185-24"},{"catalog":"ESO-LV","designation":"ESO-LV 185-0240"},{"catalog":"IC","designation":"IC 4902"},{"catalog":"LEDA","designation":"LEDA 63798"},{"catalog":"PGC","designation":"PGC 63798"}],"updated_at":"2026-10-01T09:42:28.932Z","citation":{"plain":"SpaceCatalog. IC 4902 [catalogue entry]. Data release DR1 (2026-08-21). https://spacecatalog.org/object/ic-4902","bibtex":"@misc{spacecatalog_ic-4902,\n  author       = {{SpaceCatalog}},\n  title        = {{IC 4902}},\n  howpublished = {SpaceCatalog, data release DR1 (2026-08-21)},\n  year         = {2026},\n  url          = {https://spacecatalog.org/object/ic-4902},\n  note         = {Catalogue entry, data release DR1 (2026-08-21). Values from OpenNGC.}\n}","url":"https://spacecatalog.org/object/ic-4902","release":"DR1","doi":null},"references":[],"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."}