LDSUN Subroutine

  1. astro_module.f90
  2. astro_module
  3. LDSUN

public subroutine LDSUN(p, e, em, p1)

Deflection of starlight by the Sun.

Status: support routine.

Notes

  1. The source is presumed to be sufficiently distant that its directions seen from the Sun and the observer are essentially the same.

  2. The deflection is restrained when the angle between the star and the center of the Sun is less than a threshold value, falling to zero deflection for zero separation. The chosen threshold value is within the solar limb for all solar-system applications, and is about 5 arcminutes for the case of a terrestrial observer.

History

  • IAU SOFA revision: 2016 June 16

Arguments

TypeIntentOptionalAttributesName
real(kind=wp), intent(in), dimension(3):: p

direction from observer to star (unit vector)
real(kind=wp), intent(in), dimension(3):: e

direction from Sun to observer (unit vector)
real(kind=wp), intent(in) :: em

distance from Sun to observer (au)
real(kind=wp), intent(out), dimension(3):: p1

observer to deflected star (unit vector)

Calls

proc~~ldsun~~CallsGraph proc~ldsun LDSUN proc~ld LD proc~ldsun->proc~ld proc~pdp PDP proc~ld->proc~pdp proc~pxp PXP proc~ld->proc~pxp

Called by

proc~~ldsun~~CalledByGraph proc~ldsun LDSUN proc~atciq ATCIQ proc~atciq->proc~ldsun proc~aticq ATICQ proc~aticq->proc~ldsun proc~atciqz ATCIQZ proc~atciqz->proc~ldsun proc~atci13 ATCI13 proc~atci13->proc~atciq proc~atco13 ATCO13 proc~atco13->proc~atciq proc~atic13 ATIC13 proc~atic13->proc~aticq proc~atoc13 ATOC13 proc~atoc13->proc~aticq

Contents

Source Code

LDSUN

Source Code

    subroutine LDSUN ( p, e, em, p1 )

    implicit none

    real(wp),dimension(3),intent(in) :: p !! direction from observer to star (unit vector)
    real(wp),dimension(3),intent(in) :: e !! direction from Sun to observer (unit vector)
    real(wp),intent(in) :: em !! distance from Sun to observer (au)
    real(wp),dimension(3),intent(out) :: p1 !! observer to deflected star (unit vector)

    real(wp) :: dlim

    !  Deflection limiter (smaller for distant observers).
    dlim = 1.0e-6_wp / max(em*em,1.0_wp)

    !  Apply the deflection.
    call LD ( 1.0_wp, p, p, e, em, dlim, p1 )

    end subroutine LDSUN