OBL06 Function

  1. astro_module.f90
  2. astro_module
  3. OBL06

public function OBL06(date1, date2) result(obl)

Mean obliquity of the ecliptic, IAU 2006 precession model.

Status: canonical model.

Notes

  1. The 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

 2450123.7D0        0D0        (JD method)
  2451545D0      -1421.3D0     (J2000 method)
 2400000.5D0     50123.2D0     (MJD method)
 2450123.5D0       0.2D0       (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 result is the angle between the ecliptic and mean equator of date DATE1+DATE2.

Reference

  • Hilton, J. et al., 2006, Celest.Mech.Dyn.Astron. 94, 351

History

  • IAU SOFA revision: 2009 December 15

Arguments

TypeIntentOptionalAttributesName
real(kind=wp), intent(in) :: date1

TT as a 2-part Julian Date (Note 1)
real(kind=wp), intent(in) :: date2

TT as a 2-part Julian Date (Note 1)

Return Value real(kind=wp)

obliquity of the ecliptic (radians, Note 2)


Called by

proc~~obl06~~CalledByGraph proc~obl06 OBL06 proc~pfw06 PFW06 proc~pfw06->proc~obl06 proc~p06e P06E proc~p06e->proc~obl06 proc~num06a NUM06A proc~num06a->proc~obl06 proc~ecm06 ECM06 proc~ecm06->proc~obl06 proc~pmat06 PMAT06 proc~ecm06->proc~pmat06 proc~pnm06a PNM06A proc~pnm06a->proc~pfw06 proc~bp06 BP06 proc~bp06->proc~pfw06 proc~bp06->proc~pmat06 proc~pmat06->proc~pfw06 proc~eceq06 ECEQ06 proc~eceq06->proc~ecm06 proc~pn06 PN06 proc~pn06->proc~pfw06 proc~eqec06 EQEC06 proc~eqec06->proc~ecm06 proc~gst06a GST06A proc~gst06a->proc~pnm06a proc~s06a S06A proc~s06a->proc~pnm06a proc~xys06a XYS06A proc~xys06a->proc~pnm06a proc~c2i06a C2I06A proc~c2i06a->proc~pnm06a proc~apco13 APCO13 proc~apco13->proc~pnm06a proc~pn06a PN06A proc~pn06a->proc~pn06 proc~apci13 APCI13 proc~apci13->proc~pnm06a proc~eo06a EO06A proc~eo06a->proc~pnm06a proc~pb06 PB06 proc~pb06->proc~pmat06 proc~atco13 ATCO13 proc~atco13->proc~apco13 proc~atci13 ATCI13 proc~atci13->proc~apci13 proc~atic13 ATIC13 proc~atic13->proc~apci13 proc~ee06a EE06A proc~ee06a->proc~gst06a proc~c2t06a C2T06A proc~c2t06a->proc~c2i06a proc~atoc13 ATOC13 proc~atoc13->proc~apco13

Contents

Source Code

OBL06

Source Code

    function OBL06 ( date1, date2 ) result(obl)

    implicit none

    real(wp),intent(in) :: date1 !! TT as a 2-part Julian Date (Note 1)
    real(wp),intent(in) :: date2 !! TT as a 2-part Julian Date (Note 1)
    real(wp) :: obl !! obliquity of the ecliptic (radians, Note 2)

    real(wp) :: t

    !  Interval between fundamental date J2000.0 and given date (JC).
    t = ( ( date1-dj00 ) + date2 ) / djc

    !  Mean obliquity.
    obl = ( 84381.406_wp       + &
          (   -46.836769_wp    + &
          (    -0.0001831_wp   + &
          (     0.00200340_wp  + &
          (    -0.000000576_wp + &
          (    -0.0000000434_wp ) &
                      * t ) * t ) * t ) * t ) * t ) * das2r

    end function OBL06