epb¶

erfa.epb(dj1, dj2)[source]¶

Julian Date to Besselian Epoch.

Parameters:

dj1double array
dj2double array

Returns:

c_retvaldouble array

Notes

Wraps ERFA function eraEpb. The ERFA documentation is:

- - - - - - -
 e r a E p b
- - - - - - -

Julian Date to Besselian Epoch.

Given:
   dj1,dj2    double     Julian Date (Notes 3,4)

Returned (function value):
              double     Besselian Epoch.

Notes:

1) Besselian Epoch is a method of expressing a moment in time as a
   year plus fraction.  It was superseded by Julian Year (see the
   function eraEpj).

2) The start of a Besselian year is when the right ascension of
   the fictitious mean Sun is 18h 40m, and the unit is the tropical
   year.  The conventional definition (see Lieske 1979) is that
   Besselian Epoch B1900.0 is JD 2415020.31352 and the length of the
   year is 365.242198781 days.

3) The time scale for the JD, originally Ephemeris Time, is TDB,
   which for all practical purposes in the present context is
   indistinguishable from TT.

4) The Julian Date is supplied in two pieces, in the usual ERFA
   manner, which is designed to preserve time resolution.  The
   Julian Date is available as a single number by adding dj1 and
   dj2.  The maximum resolution is achieved if dj1 is 2451545.0
   (J2000.0).

Reference:

   Lieske, J.H., 1979. Astron.Astrophys., 73, 282.

This revision:  2023 May 5

Copyright (C) 2013-2023, NumFOCUS Foundation.
Derived, with permission, from the SOFA library.  See notes at end of file.

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epb¶