Astroimager John Chumack from Dayton, Ohio, took this image of Comet ISON (C/2012 S1) on October 18, while it was near reddish Mars and blue-white Regulus (Alpha Leonis). He used a Canon Rebel XSi DSLR and a 170mm lens at f/6.3. He set the camera's speed to ISO 400, placed it on a tracking mount, and, at 6:27 a.m., started a 366-second exposure. He reported, "ISON had cleared the trees around 6 a.m., but dawn started to flood the image with light, not to mention the city lights over D.C. and strong light from a nearly Full Moon. Although the image is a bit noisy, it was the best one for that session."
John Chumack