code: def nextStationJD(ID, jd):
      
      speed = swe.sweObject(ID, jd)['lonspeed']
      for i in range(2000):
          nextjd = jd + i / 2
          nextspeed = swe.sweObject(ID, nextjd)['lonspeed']
          if speed * nextspeed <= 0:
              return nextjd
      return None
docs: Finds the aproximate julian date of the
      next station of a planet.