code: def _estimate_angle(angle, reg_coordinate_frame, header):
      
      y_axis_rot = _calculate_rotation_angle(reg_coordinate_frame, header)
      return angle - y_axis_rot
docs: Transform an angle into a different frame
  
      Parameters
      ----------
      angle : float, int
          The number of degrees, measured from the Y axis in origin's frame
  
      reg_coordinate_frame : str
          Coordinate frame in which ``angle`` is defined
  
      header : `~astropy.io.fits.Header` instance
          Header describing the image
  
      Returns
      -------
      angle : float
          The angle, measured from the Y axis in the WCS defined by ``header'`