XMM-Newton Science Analysis System


ssclib (ssclib-4.36.3) [22.0.0-9173c7d25-20250127]

tanToRaDec

  interface tanToRaDec
    subroutine tanToRaDecScalar(refRaDeg, refDecDeg, tanX, tanY, raDeg, decDeg)
      real(double), intent(in)  :: refRaDeg,&
                                   refDecDeg,&
                                   tanX,&
                                   tanY
      real(double), intent(out) :: raDeg,&
                                   decDeg
    end subroutine tanToRaDecScalar

    subroutine tanToRaDecVector(refRaDeg, refDecDeg, tanX, tanY, raDeg, decDeg)
      real(double), intent(in)  :: refRaDeg,&
                                   refDecDeg,&
                                   tanX(:),&
                                   tanY(size(tanX))
      real(double), intent(out) :: raDeg(size(tanX)),&
                                   decDeg(size(tanX))
  end interface

! tanToRaDecArray not yet done

This transform is a projection to celestial coordinates from that tangent plane normal to the direction defined by refRaDeg and refDecDeg. The signs of the the returned values are such that tanX increases in the direction of decreasing ra and tanY increases in the direction of increasing dec. If the tangent plane were viewed from the centre of the celestial sphere, with the celestial north pole at the zenith, tanX would increase to rightwards and tanY upwards.