import numpy
import astropy
from astropy.io import fits as pyfits

FitsFile = pyfits.open('M33.fits')

image = FitsFile[0].data
header =FitsFile[0].header

FitsFile.close()

sizez = image.shape[0]
sizey = image.shape[1]
sizex = image.shape[2]

newimage = numpy.zeros_like(image)


for i in range(sizex):
	for j in range(sizey):
		for k in range(sizez):
			if image[k, j, i] <= 0.01:
				newimage[k, j, i] = image[k, j, i]
			else:
				newimage[k, j, i] = 0.01
		

newfitsfile = 'M33MaskSecondaryVolume.fits'

pyfits.writeto(newfitsfile, newimage, header=header)