Ok this is the veil nebula 10 stacked frames of 10 min. 20 dark frames, 20 light frames gain at 310 raw 16 I stacked them in deep sky stacker. When I loaded the image in pixnsight and used the screen transfer function to stretch using the radioactive icon. When I zoom in I get these black squares. Have anyone encountered this. I went back an looked at other images and some have them and some do not. any ideas why this would happen. The attached pic is of the zoomed in pic to see the black squares.