{
  "id": "astro-sdss-0358-51818-0270@1",
  "version": 1,
  "checked": "2026-10-30",
  "source": "https://data.sdss.org/sas/dr17/sdss/spectro/redux/26/spectra/0358/spec-0358-51818-0270.fits",
  "release": "DR17 archived public release, not a claim of latest release",
  "sourceSha256": "4d8d3f50a17b48b7aec7da068a298a48e955a0b8411ab206e63a85c1b63b2f3d",
  "sourceBytes": 748800,
  "credit": "Sloan Digital Sky Survey; legacy SDSS-I/II observation distributed in DR17, RUN2D 26",
  "reuse": "Public-release SDSS data are considered public domain under the collaboration policy; attribution and source link retained. Course is not endorsed by SDSS.",
  "reuseUrl": "https://sdss.org/collaboration",
  "acknowledgmentUrls": [
    "https://classic.sdss.org/collaboration/credits.html",
    "https://www.sdss4.org/collaboration/citing-sdss/"
  ],
  "schema": "https://data.sdss.org/datamodel/files/SPECTRO_REDUX/RUN2D/spectra/PLATE4/spec.html",
  "fieldContext": "https://www.sdss4.org/dr17/spectro/spectro_basics/",
  "maskContext": "https://www.sdss4.org/dr17/spectro/quality/",
  "maskBits": "https://www.sdss4.org/dr17/algorithms/bitmasks/",
  "plate": 358,
  "mjd": 51818,
  "fiber": 270,
  "run2d": "26",
  "specObjId": "403146414185539584",
  "targetRaDegrees": 262.09951,
  "targetDecDegrees": 56.250173,
  "pipelineClass": "QSO",
  "pipelineRedshift": 2.1095004081726074,
  "pipelineRedshiftError": 0.0006861310102976859,
  "pipelineZwarning": 0,
  "metadataBoundary": "Pipeline class/redshift are disclosed source labels, not learner independent identification. QSO cosmological redshift must not be converted to peculiar velocity using cz or a special-relativistic isolated-source formula.",
  "hdu": "HDU1 COADD binary table; 3819 rows, 32 bytes/row; fields big-endian float32,float32,float32,int32,int32,float32,float32,float32. Data starts at byte14400 in this exact hashed file; offsets are not general FITS assumptions.",
  "units": {
    "flux": "10^-17 erg s^-1 cm^-2 Angstrom^-1",
    "loglam": "log10 heliocentric vacuum wavelength in Angstrom",
    "ivar": "inverse squared source flux units",
    "and_mask": "integer bitwise AND across exposure flags",
    "or_mask": "integer bitwise OR across exposure flags",
    "wdisp": "source wavelength dispersion in pixels; retained without conversion in this category",
    "sky": "source flux-density units",
    "model": "source flux-density units; pipeline model, not independent observation"
  },
  "selection": "Four fixed index windows of16 consecutive COADD rows, starts0,1000,2000,3000. No flux, line, quality or class filtering before selection. Full3819-row CSV also supplied. Overview takes every30th row plus last; not an integrated/rebinned spectrum and cannot recover narrow features.",
  "calibrationCaveat": "Use actual per-row LOGLAM for wavelength. The primary header COEFF0=3.5781 describes a wider grid; this trimmed single-object table starts at LOGLAM\u22483.5817000866. Do not attach the primary untrimmed offset to row0.",
  "maskPolicies": "Compare ivar-positive only, additionally AND_MASK=0, or additionally OR_MASK=0 as explicit pedagogical sensitivity screens, not universal SDSS recommendations. Nonzero flags have different meanings; preserving them is essential. No surviving rows means no estimate, not zero flux.",
  "uncertainty": "Formal weighted-mean error assumes independent pixels and a locally constant flux model. Coaddition/resampling, covariance, calibration systematics and real spectral structure can invalidate it; this is not a new astrophysical fit."
}