code: def ra_dec_to_cartesian(
              self,
              ra,
              dec):
          
          self.log.info('starting the ``ra_dec_to_cartesian`` method')
  
          ra = self.ra_sexegesimal_to_decimal(
              ra=ra
          )
          dec = self.dec_sexegesimal_to_decimal(
              dec=dec
          )
  
          ra = math.radians(ra)
          dec = math.radians(dec)
          cos_dec = math.cos(dec)
          cx = math.cos(ra) * cos_dec
          cy = math.sin(ra) * cos_dec
          cz = math.sin(dec)
  
          cartesians = (cx, cy, cz)
  
          self.log.info('completed the ``ra_dec_to_cartesian`` method')
          return cartesians
docs: *Convert an RA, DEC coordinate set to x, y, z cartesian coordinates*
  
          **Key Arguments:**
              - ``ra`` -- right ascension in sexegesimal or decimal degress.
              - ``dec`` -- declination in sexegesimal or decimal degress.
  
          **Return:**
              - ``cartesians`` -- tuple of (x, y, z) coordinates
  
          ..  todo::
  
              - replace calculate_cartesians in all code
  
          **Usage:**
  
              .. code-block:: python 
  
                  from astrocalc.coords import unit_conversion
                  converter = unit_conversion(
                      log=log
                  )
                  x, y, z = converter.ra_dec_to_cartesian(
                      ra="23 45 21.23232",
                      dec="+01:58:5.45341"
                  )
                  print x, y, z
  
                  # OUTPUT: 0.9973699780687104, -0.06382462462791459, 0.034344492110465606