fk5hz¶
- erfa.fk5hz(r5, d5, date1, date2)[source]¶
Transform an FK5 (J2000.0) star position into the system of the Hipparcos catalog, assuming zero Hipparcos proper motion.
- Parameters:
- r5double array
- d5double array
- date1double array
- date2double array
- Returns:
- rhdouble array
- dhdouble array
Notes
Wraps ERFA function
eraFk5hz
. The ERFA documentation is:- - - - - - - - - e r a F k 5 h z - - - - - - - - - Transform an FK5 (J2000.0) star position into the system of the Hipparcos catalog, assuming zero Hipparcos proper motion. Given: r5 double FK5 RA (radians), equinox J2000.0, at date d5 double FK5 Dec (radians), equinox J2000.0, at date date1,date2 double TDB date (Notes 1,2) Returned: rh double Hipparcos RA (radians) dh double Hipparcos Dec (radians) Notes: 1) This function converts a star position from the FK5 system to the Hipparcos system, in such a way that the Hipparcos proper motion is zero. Because such a star has, in general, a non-zero proper motion in the FK5 system, the function requires the date at which the position in the FK5 system was determined. 2) The TT date date1+date2 is a Julian Date, apportioned in any convenient way between the two arguments. For example, JD(TT)=2450123.7 could be expressed in any of these ways, among others: date1 date2 2450123.7 0.0 (JD method) 2451545.0 -1421.3 (J2000 method) 2400000.5 50123.2 (MJD method) 2450123.5 0.2 (date & time method) The JD method is the most natural and convenient to use in cases where the loss of several decimal digits of resolution is acceptable. The J2000 method is best matched to the way the argument is handled internally and will deliver the optimum resolution. The MJD method and the date & time methods are both good compromises between resolution and convenience. 3) The FK5 to Hipparcos transformation is modeled as a pure rotation and spin; zonal errors in the FK5 catalog are not taken into account. 4) The position returned by this function is in the Hipparcos reference system but at date date1+date2. 5) See also eraFk52h, eraH2fk5, eraHfk5z. Called: eraS2c spherical coordinates to unit vector eraFk5hip FK5 to Hipparcos rotation and spin eraSxp multiply p-vector by scalar eraRv2m r-vector to r-matrix eraTrxp product of transpose of r-matrix and p-vector eraPxp vector product of two p-vectors eraC2s p-vector to spherical eraAnp normalize angle into range 0 to 2pi Reference: F.Mignard & M.Froeschle, 2000, Astron.Astrophys. 354, 732-739. This revision: 2023 March 6 Copyright (C) 2013-2023, NumFOCUS Foundation. Derived, with permission, from the SOFA library. See notes at end of file.