from astropy.io import fits
import csv
import os

def norm_psf(filename):
  hdulist1 = fits.open(filename)
  dat = hdulist1[0].data
  print sum(sum(dat))
  dat = dat / sum(sum(dat))
  hdu = fits.PrimaryHDU(data=dat)
  hdulist = fits.HDUList([hdu])
  hdulist.writeto(filename, clobber=True)
  hdulist1.close()