| 1 | #include "slalib.h"
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| 2 | #include "slamac.h"
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| 3 | void slaAmp ( double ra, double da, double date, double eq,
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| 4 | double *rm, double *dm )
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| 5 | /*
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| 6 | ** - - - - - - -
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| 7 | ** s l a A m p
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| 8 | ** - - - - - - -
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| 9 | **
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| 10 | ** Convert star RA,Dec from geocentric apparent to mean place.
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| 11 | **
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| 12 | ** The mean coordinate system is the post IAU 1976 system,
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| 13 | ** loosely called FK5.
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| 14 | **
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| 15 | ** Given:
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| 16 | ** ra double apparent RA (radians)
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| 17 | ** da double apparent Dec (radians)
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| 18 | ** date double TDB for apparent place (JD-2400000.5)
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| 19 | ** eq double equinox: Julian epoch of mean place
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| 20 | **
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| 21 | ** Returned:
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| 22 | ** *rm double mean RA (radians)
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| 23 | ** *dm double mean Dec (radians)
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| 24 | **
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| 25 | ** References:
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| 26 | ** 1984 Astronomical Almanac, pp B39-B41.
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| 27 | ** (also Lederle & Schwan, Astron. Astrophys. 134, 1-6, 1984)
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| 28 | **
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| 29 | ** Notes:
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| 30 | **
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| 31 | ** 1) The distinction between the required TDB and the more
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| 32 | ** accessible TT is always negligible. Moreover, for all
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| 33 | ** but the most critical applications UTC is adequate.
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| 34 | **
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| 35 | ** 2) The accuracy is limited by the routine slaEvp, called
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| 36 | ** by slaMappa, which computes the Earth positions and
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| 37 | ** velocities using the methods of Stumpff. The maximum
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| 38 | ** error is about 0.3 milliarcsecond.
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| 39 | **
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| 40 | ** 3) Iterative techniques are used for the aberration and
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| 41 | ** light deflection corrections so that the routines
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| 42 | ** slaAmp (or slaAmpqk) and slaMap (or slaMapqk) are
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| 43 | ** accurate inverses; even at the edge of the Sun's disc
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| 44 | ** the discrepancy is only about 1 nanoarcsecond.
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| 45 | **
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| 46 | ** 4) Where multiple apparent places are to be converted to
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| 47 | ** mean places, for a fixed date and equinox, it is more
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| 48 | ** efficient to use the slaMappa routine to compute the
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| 49 | ** required parameters once, followed by one call to
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| 50 | ** slaAmpqk per star.
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| 51 | **
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| 52 | ** Called: slaMappa, slaAmpqk
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| 53 | **
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| 54 | ** Last revision: 12 June 1996
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| 55 | **
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| 56 | ** Copyright P.T.Wallace. All rights reserved.
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| 57 | **
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| 58 | */
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| 59 | {
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| 60 | double amprms[21]; /* Mean-to-apparent parameters */
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| 61 |
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| 62 | slaMappa ( eq, date, amprms );
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| 63 | slaAmpqk ( ra, da, amprms, rm, dm );
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| 64 | }
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