Opening the files in DS9
In DS9, go to File > Open and select the first FITS file you wish to open. Click ‘Ok’. You will then see a screen similar to the one here. There is no obvious image in this FITS file, and the screen is mostly black. Here, DS9 is displaying the full range of pixel values in the image, from 0 to 65,000. In order to make the image more visible, we use the ‘Scale’ option from the menu bar. Select Scale and 99%.