docs: def create_pointing(self,event):
          """Plot the sky coverage of pointing at event.x,event.y on the canavas"""
  
          import math
          (ra,dec)=self.c2p((self.canvasx(event.x),
                             self.canvasy(event.y)))
          this_camera=camera(camera=self.camera.get())
          ccds=this_camera.getGeometry(ra,dec)
          items=[]
          for ccd in ccds:
              (x1,y1)=self.p2c((ccd[0],ccd[1]))
              (x2,y2)=self.p2c((ccd[2],ccd[3]))
              item=self.create_rectangle(x1,y1,x2,y2)
              items.append(item)
  	label={}
  	label['text']=w.plabel.get()
  	label['id']=self.label(this_camera.ra,this_camera.dec,label['text'])
          self.pointings.append({
  		"label": label,
  		"items": items,
  		"camera": this_camera} )
          self.current_pointing(len(self.pointings)-1)