function jd_bo_fn, xx

;Converts from (Julian date -2440000) to B angle

incl = double(7.25)

  JD_DD = double(xx) 

  ;nn = JD_DD - 2451545.0
  ; 2440000 - 2451545 = 11545
  nn = JD_DD - double(11545.0)
  LL = double(280.472) + double(0.9856474)*nn
  gg = double(357.528) + double(0.9856003)*nn
  sun = LL + double(1.915)*sin(gg*!pi/double(180.0)) $
  + double(0.020)*sin(double(2.0)*gg*!pi/double(180.0))

; Explains where the number 43243.25 comes from
; omega = 73.0 + 40.0/60.0+ 50.25*(JD_DD + 2440000.0 - $
; 2396756.75)/365.25)/3600.0

  omega = double(73.0) + double(40.0)/double(60.0)+$
  double(50.25)*((JD_DD + double(43243.25))/double(365.25))/double(3600.0)

; Explains where the number 41780.0 comes from
; ww = 360.0/25.38*(JD_DD+2440000.0 - 2398220.0)

  ww = double(360.0)/double(25.38)*(JD_DD+double(41780.0))
  ww = (ww/double(360.0) - long(ww/double(360.0)))*double(360.0)

  Bosin = sin((sun-omega)*!pi/double(180.0))*sin(incl*!pi/double(180.0))
  Bocos = sqrt(double(1.0) - Bosin^2)

  Bo = atan(Bosin,Bocos)*double(180.0)/!pi

  LoWsin = cos(incl*!pi/double(180.0))*sin((omega-sun)*!pi/double(180.0))/cos(Bo*!pi/double(180.0))
  LoWcos = -cos((omega-sun)*!pi/180.0)/cos(Bo*!pi/180.0)
  LoW = atan(LoWsin,LoWcos)*double(180.0)/!pi

  if LoW lt 0.0 then LoW = LoW + double(360.0)
     Lo = LoW - ww

  if Lo lt 0.0 then Lo = Lo + double(360.0)

  return,Bo

end