code: def create_skydir_ltcube(self, skydir, tab_sc, tab_gti, zmax):
          
  
          skydir = SkyCoord(np.array([skydir.ra.deg]),
                            np.array([skydir.dec.deg]), unit='deg')
  
          lt, lt_wt = fill_livetime_hist(skydir, tab_sc, tab_gti, zmax,
                                         self.costh_edges)
  
          ipix = self.hpx.skydir_to_pixel(skydir)
  
          lt_scale = np.ones_like(lt)
          lt_wt_scale = np.ones_like(lt_wt)
          m = self.data[:, ipix] > 0.0
  
          lt_scale[m] = lt[m] / self.data[:, ipix][m]
          lt_wt_scale[m] = lt_wt[m] / self._data_wt[:, ipix][m]
          data = self.data * lt_scale
          data_wt = self._data_wt * lt_wt_scale
          return LTCube(data, copy.deepcopy(self.hpx), self.costh_edges,
                        # tstart=np.min(tab_gti_t0),
                        # tstop=np.max(tab_gti_t1),
                        zmax=zmax, data_wt=data_wt)
docs: Create a new livetime cube by scaling this one by the
          observing profile ratio in the direction ``skydir``.  This
          method can be used to generate an approximate livetime cube
          that is accurate in the vicinity of ``skydir``.
  
          Parameters
          ----------
          skydir :  `~astropy.coordinates.SkyCoord`
  
          tab_sc : `~astropy.table.Table`
              Spacecraft (FT2) table.
  
          tab_gti : `~astropy.table.Table`
              Table of GTIs.
  
          zmax : float
              Zenith angle cut.