eo06a¶
- erfa.eo06a(date1, date2)[source]¶
Equation of the origins, IAU 2006 precession and IAU 2000A nutation.
- Parameters:
- date1double array
- date2double array
- Returns:
- c_retvaldouble array
Notes
Wraps ERFA function
eraEo06a
. The ERFA documentation is:- - - - - - - - - e r a E o 0 6 a - - - - - - - - - Equation of the origins, IAU 2006 precession and IAU 2000A nutation. Given: date1,date2 double TT as a 2-part Julian Date (Note 1) Returned (function value): double the equation of the origins in radians Notes: 1) 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. 2) The equation of the origins is the distance between the true equinox and the celestial intermediate origin and, equivalently, the difference between Earth rotation angle and Greenwich apparent sidereal time (ERA-GST). It comprises the precession (since J2000.0) in right ascension plus the equation of the equinoxes (including the small correction terms). Called: eraPnm06a classical NPB matrix, IAU 2006/2000A eraBpn2xy extract CIP X,Y coordinates from NPB matrix eraS06 the CIO locator s, given X,Y, IAU 2006 eraEors equation of the origins, given NPB matrix and s References: Capitaine, N. & Wallace, P.T., 2006, Astron.Astrophys. 450, 855 Wallace, P.T. & Capitaine, N., 2006, Astron.Astrophys. 459, 981 This revision: 2021 May 11 Copyright (C) 2013-2023, NumFOCUS Foundation. Derived, with permission, from the SOFA library. See notes at end of file.