code: def to_df(self):
          
          df = pd.DataFrame()
          name = []
          band = []
          resolution = []
          mag = []
          e_mag = []
          separation = []
          pa = []
          relative = []
          for o in self._observations:
              for s in o.sources:
                  name.append(o.name)
                  band.append(o.band)
                  resolution.append(o.resolution)
                  mag.append(s.mag)
                  e_mag.append(s.e_mag)
                  separation.append(s.separation)
                  pa.append(s.pa)
                  relative.append(s.relative)
  
          return pd.DataFrame({'name':name,'band':band,'resolution':resolution,
                               'mag':mag,'e_mag':e_mag,'separation':separation,
                               'pa':pa,'relative':relative})
docs: Returns DataFrame with photometry from observations organized.
  
          This DataFrame should be able to be read back in to
          reconstruct the observation.