The hard band (0.5–2.0 keV) mosaic of the Cygnus Loop (left panel) and the hard/soft band ratio (0.5–2.0/0.1–0.3 keV) of the remnant (right panel) obtained with ROSAT (Levenson, Graham & Snowden 1999). This image has been downloaded from http://imagine.gsfc.nasa.gov/Images/rosat/snr_cygloop.html. (Credit: S. L. Snowden)