I've found this little program great for viewing the FITS header without having to open the image.
http://arnholm.org/astro/software/ImageTOOLSca/
There are two programs in the download, a viewer and a reader. After a while the viewer license expires (unless you pay for it of course
) but the reader keeps working. It allows you to open one header and then click to the next without going back to the image and opening the header. It is a very handy little stand alone.
