{
  "schema": 1,
  "reference": "NASA/JPL Horizons DE441, airless topocentric observer tables retrieved 2026-10-02",
  "reference_sampling": "339 instants per body, separated by 414 hours, from 2020-01-01T07:00:00Z through 2035-12-18T19:00:00Z; not exhaustive validation of every instant",
  "valid_local_years": [
    2020,
    2035
  ],
  "timezone": "America/Denver",
  "location": {
    "name": "Sunset Point, Bryce Canyon",
    "latitude": 37.622568,
    "longitude": -112.165988,
    "heightMeters": 0,
    "zone": "America/Denver"
  },
  "teaching_tolerances": {
    "star_position_deg": 0.1,
    "sun_position_deg": 0.1,
    "moon_position_deg": 0.25,
    "moon_illumination_percentage_points": 2
  },
  "sampled_errors": {
    "sun": {
      "cases": 339,
      "max_angular_error_deg": 0.014842350810171693,
      "worst_angular_case": "2026-03-10T01:00:00Z",
      "max_altitude_error_deg": 0.014451077482006802
    },
    "moon": {
      "cases": 339,
      "max_angular_error_deg": 0.09553968421750253,
      "worst_angular_case": "2032-07-24T19:00:00Z",
      "max_altitude_error_deg": 0.06918379040025258,
      "max_phase_error_percentage_points": 0.8121851015890371
    }
  },
  "max_mean_vs_apparent_sidereal_error_deg": 0.0057943312810948555,
  "star_error_basis": "J2000 catalogue precession independently checked against ERFA/SOFA pmat76. Largest catalogue proper motion omitted is 5280.652 mas/year, under 0.053 degree through 2035. The 0.1 degree teaching allowance also covers omitted nutation, annual aberration, parallax and UTC/UT1 approximation. Catalogue errors are not independently remeasured.",
  "conventions": [
    "Angles in degrees; RA converted from catalogue hours",
    "North-positive latitude, east-positive longitude",
    "Azimuth north=0, east=90, south=180, west=270",
    "Geometric altitude, no refraction or terrain",
    "Mean equator/equinox of date for stars; approximate of-date solar/lunar positions",
    "UTC approximates UT1; solar/lunar formulas do not distinguish TT and UT",
    "Moon uses WGS84 observer vector at zero ellipsoid height; this is a small approximation, not actual Bryce elevation",
    "Moon phase is geocentric; JPL comparison is observer-relative"
  ],
  "independent_tests": [
    "Meeus 1987-04-10 GMST worked example",
    "ERFA/SOFA pmat76 published matrix",
    "Analytic horizon, zenith, east/west and polar cases",
    "678 JPL Sun/Moon rows and horizon-side comparisons",
    "ESA Galactic-center transformation case"
  ],
  "limitations": [
    "Samples are not an exhaustive error proof",
    "Uncertainty near the horizon is dominated by unmodeled refraction and skyline",
    "Predicted future Earth orientation and current browser time-zone rules are assumed",
    "No telescope pointing, eclipses, occultations, exact rise/set times or observing guarantees",
    "No independent astronomer or field review"
  ],
  "pass": true,
  "first_reference_utc": "2020-01-01T07:00:00Z",
  "last_reference_utc": "2035-12-18T19:00:00Z"
}