R-band optical image of the diffuse X-ray source 3XMM J204914.4+290324 obtained on the Hiltner telescope. The field displayed is 3′ × 3′. The 45″ radius circle encompasses most of the X-ray emission. At the center is the galaxy 2MASX J20491447+2903237, the dominant galaxy of a cluster whose fainter members can also be seen in this image.