code: def getChannelColRow(self, ra, dec, wantZeroOffset=False,
                           allowIllegalReturnValues=True):
          
          try:
              ch = self.pickAChannel(ra, dec)
          except ValueError:
              logger.warning("WARN: %.7f %.7f not on any channel" % (ra, dec))
              return (0, 0, 0)
  
          col, row = self.getColRowWithinChannel(ra, dec, ch, wantZeroOffset,
                                                 allowIllegalReturnValues)
          return (ch, col, row)
docs: Returns (channel, column, row) given an (ra, dec) coordinate.
  
          Returns (0, 0, 0) or a ValueError if the coordinate is not on silicon.