code: def offset_to_sky(skydir, offset_lon, offset_lat,
                    coordsys='CEL', projection='AIT'):
      
  
      offset_lon = np.array(offset_lon, ndmin=1)
      offset_lat = np.array(offset_lat, ndmin=1)
  
      w = create_wcs(skydir, coordsys, projection)
      pixcrd = np.vstack((offset_lon, offset_lat)).T
  
      return w.wcs_pix2world(pixcrd, 0)
docs: Convert a cartesian offset (X,Y) in the given projection into
      a pair of spherical coordinates.