Ryan Malloy
0544a78276
Phase 1 — Stars, comets, Keplerian propagation: - star_observe() / star_observe_safe(): fixed star alt/az via IAU 1976 precession, equatorial-to-horizontal transform - kepler_propagate(): two-body Keplerian orbit propagation for elliptic, parabolic, and hyperbolic orbits - comet_observe(): observe comets/asteroids from orbital elements - heliocentric type: ecliptic J2000 position (x, y, z in AU) Phase 2 — VSOP87 planets, ELP82B Moon, Sun: - planet_heliocentric(): VSOP87 heliocentric ecliptic J2000 positions for Mercury through Neptune (Bretagnon & Francou, MIT) - planet_observe(): full observation pipeline for any planet - sun_observe(): Sun position from negated Earth VSOP87 - moon_observe(): ELP2000-82B lunar position (Chapront-Touzé, MIT) - Clean-room precession (IAU 2006) and sidereal time (IERS 2010) - elliptic_to_rectangular utility (Stellarium, MIT) All Stellarium extractions are MIT-licensed, thread-safe (static caching removed for PARALLEL SAFE), zero external data files. All 9 regression tests pass (90ms total).
123 lines
3.6 KiB
C
123 lines
3.6 KiB
C
/*
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* star_funcs.c -- Star and fixed-position object observation
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*
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* Takes J2000 catalog coordinates (RA in hours, Dec in degrees),
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* applies IAU 1976 precession to date of observation, computes
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* local hour angle, and converts to topocentric azimuth/elevation.
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*
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* Range and range_rate are zero -- stars are effectively at infinity.
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* For objects with known proper motion, apply it to (RA, Dec) before
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* calling star_observe.
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*/
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#include "postgres.h"
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#include "fmgr.h"
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#include "utils/timestamp.h"
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#include "types.h"
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#include "astro_math.h"
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PG_FUNCTION_INFO_V1(star_observe);
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PG_FUNCTION_INFO_V1(star_observe_safe);
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/*
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* star_observe(ra_hours, dec_degrees, observer, timestamptz) -> topocentric
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*
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* Compute az/el of a fixed celestial object from an observer at a time.
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* Uses IAU 1976 precession (~1 arcsecond accuracy for centuries near J2000).
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*/
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Datum
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star_observe(PG_FUNCTION_ARGS)
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{
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double ra_hours = PG_GETARG_FLOAT8(0);
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double dec_deg = PG_GETARG_FLOAT8(1);
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pg_observer *obs = (pg_observer *) PG_GETARG_POINTER(2);
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int64 ts = PG_GETARG_INT64(3);
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double jd;
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double ra_j2000, dec_j2000;
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double ra_date, dec_date;
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double gmst, lst, ha;
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double az, el;
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pg_topocentric *result;
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if (ra_hours < 0.0 || ra_hours >= 24.0)
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ereport(ERROR,
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(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
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errmsg("right ascension out of range: %.6f", ra_hours),
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errhint("RA must be in [0, 24) hours.")));
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if (dec_deg < -90.0 || dec_deg > 90.0)
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ereport(ERROR,
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(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
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errmsg("declination out of range: %.6f", dec_deg),
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errhint("Declination must be between -90 and +90 degrees.")));
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jd = timestamptz_to_jd(ts);
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ra_j2000 = ra_hours * (M_PI / 12.0);
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dec_j2000 = dec_deg * DEG_TO_RAD;
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precess_j2000_to_date(jd, ra_j2000, dec_j2000, &ra_date, &dec_date);
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gmst = gmst_from_jd(jd);
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lst = gmst + obs->lon;
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ha = lst - ra_date;
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equatorial_to_horizontal(ha, dec_date, obs->lat, &az, &el);
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result = (pg_topocentric *) palloc(sizeof(pg_topocentric));
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result->azimuth = az;
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result->elevation = el;
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result->range_km = 0.0;
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result->range_rate = 0.0;
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PG_RETURN_POINTER(result);
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}
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/*
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* star_observe_safe -- returns NULL if inputs are out of range.
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* For batch queries over star catalogs.
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*/
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Datum
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star_observe_safe(PG_FUNCTION_ARGS)
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{
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double ra_hours = PG_GETARG_FLOAT8(0);
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double dec_deg = PG_GETARG_FLOAT8(1);
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pg_observer *obs = (pg_observer *) PG_GETARG_POINTER(2);
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int64 ts = PG_GETARG_INT64(3);
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double jd;
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double ra_j2000, dec_j2000;
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double ra_date, dec_date;
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double gmst, lst, ha;
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double az, el;
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pg_topocentric *result;
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if (ra_hours < 0.0 || ra_hours >= 24.0)
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PG_RETURN_NULL();
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if (dec_deg < -90.0 || dec_deg > 90.0)
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PG_RETURN_NULL();
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jd = timestamptz_to_jd(ts);
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ra_j2000 = ra_hours * (M_PI / 12.0);
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dec_j2000 = dec_deg * DEG_TO_RAD;
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precess_j2000_to_date(jd, ra_j2000, dec_j2000, &ra_date, &dec_date);
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gmst = gmst_from_jd(jd);
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lst = gmst + obs->lon;
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ha = lst - ra_date;
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equatorial_to_horizontal(ha, dec_date, obs->lat, &az, &el);
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result = (pg_topocentric *) palloc(sizeof(pg_topocentric));
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result->azimuth = az;
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result->elevation = el;
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result->range_km = 0.0;
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result->range_rate = 0.0;
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PG_RETURN_POINTER(result);
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}
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