docs: def create_pointing(self, event, label_text=None):
          """Plot the sky coverage of pointing at event.x,event.y on the canvas.
  
          """
          x = self.canvasx(event.x)
          y = self.canvasy(event.y)
          (ra, dec) = self.c2p((x, y))
          this_camera = Camera(ra=float(ra) * units.radian, dec=float(dec)*units.radian, camera=self.camera.get())
  
          ccds = numpy.radians(numpy.array(this_camera.geometry))
          items = []
          for ccd in ccds:
              if len(ccd) == 4:
                  (x1, y1) = self.p2c((ccd[0], ccd[1]))
                  (x2, y2) = self.p2c((ccd[2], ccd[3]))
                  item = self.create_rectangle(x1, y1, x2, y2, stipple='gray25', fill=None)
              else:
                  (x1, y1) = self.p2c((ccd[0] - ccd[2], ccd[1] - ccd[2]))
                  (x2, y2) = self.p2c((ccd[0] + ccd[2], ccd[1] + ccd[2]))
                  item = self.create_oval(x1, y1, x2, y2)
              items.append(item)
          label = {}
          if label_text is None:
              label_text = self.plabel.get()
          label['text'] = label_text
          label['id'] = self.label(this_camera.ra.radian, this_camera.dec.radian, label['text'])
          self.pointings.append({
              "label": label,
              "items": items,
              "camera": this_camera})
          self.current = len(self.pointings) - 1
          self.current_pointing(len(self.pointings) - 1)