code: def pickAChannel(self, ra_deg, dec_deg):
          
          # Could improve speed by doing this in the projection plane
          # instead of sky coords
          cRa = self.currentRaDec[:, 3]  # Ra of each channel corner
          cDec = self.currentRaDec[:, 4]  # dec of each channel corner
  
          dist = cRa * 0
          for i in range(len(dist)):
              dist[i] = gcircle.sphericalAngSep(cRa[i], cDec[i], ra_deg, dec_deg)
  
          i = np.argmin(dist)
          return self.currentRaDec[i, 2]
docs: Returns the channel number closest to a given (ra, dec) coordinate.