lteceq¶
- erfa.lteceq(epj, dl, db)[source]¶
Transformation from ecliptic coordinates (mean equinox and ecliptic of date) to ICRS RA,Dec, using a long-term precession model.
- Parameters:
- epjdouble array
- dldouble array
- dbdouble array
- Returns:
- drdouble array
- dddouble array
Notes
Wraps ERFA function
eraLteceq
. The ERFA documentation is:- - - - - - - - - - e r a L t e c e q - - - - - - - - - - Transformation from ecliptic coordinates (mean equinox and ecliptic of date) to ICRS RA,Dec, using a long-term precession model. Given: epj double Julian epoch (TT) dl,db double ecliptic longitude and latitude (radians) Returned: dr,dd double ICRS right ascension and declination (radians) 1) No assumptions are made about whether the coordinates represent starlight and embody astrometric effects such as parallax or aberration. 2) The transformation is approximately that from ecliptic longitude and latitude (mean equinox and ecliptic of date) to mean J2000.0 right ascension and declination, with only frame bias (always less than 25 mas) to disturb this classical picture. 3) The Vondrak et al. (2011, 2012) 400 millennia precession model agrees with the IAU 2006 precession at J2000.0 and stays within 100 microarcseconds during the 20th and 21st centuries. It is accurate to a few arcseconds throughout the historical period, worsening to a few tenths of a degree at the end of the +/- 200,000 year time span. Called: eraS2c spherical coordinates to unit vector eraLtecm J2000.0 to ecliptic rotation matrix, long term eraTrxp product of transpose of r-matrix and p-vector eraC2s unit vector to spherical coordinates eraAnp normalize angle into range 0 to 2pi eraAnpm normalize angle into range +/- pi References: Vondrak, J., Capitaine, N. and Wallace, P., 2011, New precession expressions, valid for long time intervals, Astron.Astrophys. 534, A22 Vondrak, J., Capitaine, N. and Wallace, P., 2012, New precession expressions, valid for long time intervals (Corrigendum), Astron.Astrophys. 541, C1 This revision: 2021 May 11 Copyright (C) 2013-2023, NumFOCUS Foundation. Derived, with permission, from the SOFA library. See notes at end of file.