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.

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lteceq¶