pmpx¶
- erfa.pmpx(rc, dc, pr, pd, px, rv, pmt, pob)[source]¶
Proper motion and parallax.
- Parameters:
- rcdouble array
- dcdouble array
- prdouble array
- pddouble array
- pxdouble array
- rvdouble array
- pmtdouble array
- pobdouble array
- Returns:
- pcodouble array
Notes
Wraps ERFA function
eraPmpx
. The ERFA documentation is:- - - - - - - - e r a P m p x - - - - - - - - Proper motion and parallax. Given: rc,dc double ICRS RA,Dec at catalog epoch (radians) pr double RA proper motion (radians/year, Note 1) pd double Dec proper motion (radians/year) px double parallax (arcsec) rv double radial velocity (km/s, +ve if receding) pmt double proper motion time interval (SSB, Julian years) pob double[3] SSB to observer vector (au) Returned: pco double[3] coordinate direction (BCRS unit vector) Notes: 1) The proper motion in RA is dRA/dt rather than cos(Dec)*dRA/dt. 2) The proper motion time interval is for when the starlight reaches the solar system barycenter. 3) To avoid the need for iteration, the Roemer effect (i.e. the small annual modulation of the proper motion coming from the changing light time) is applied approximately, using the direction of the star at the catalog epoch. References: 1984 Astronomical Almanac, pp B39-B41. Urban, S. & Seidelmann, P. K. (eds), Explanatory Supplement to the Astronomical Almanac, 3rd ed., University Science Books (2013), Section 7.2. Called: eraPdp scalar product of two p-vectors eraPn decompose p-vector into modulus and direction This revision: 2021 April 3 Copyright (C) 2013-2023, NumFOCUS Foundation. Derived, with permission, from the SOFA library. See notes at end of file.