Latest Development: As of January 23rd, the waxing crescent Moon makes further sightings of the comet's tail from the Northern Hemisphere unlikely.
It's been several days since anyone in the Northern Hemisphere saw the head of Comet McNaught. But the comet's tail is so bright and long that numerous northern observers have spotted it in a dark sky two or more hours after the head has set. Nothing like this has been seen since Jean-Philippe Loys de Cheseaux sketched the tip of a comet's tail protruding above the horizon in 1744.
Dan Laszlo of the Northern Colorado Astronomical Society urges all experienced observers to get far away from any city and look to the west an hour or two after sunset. A site where the zodiacal light is clearly visible is best. Binoculars are helpful, but the tail was still visible to the unaided eye on the evening of January 19th. Laszlo stresses that even negative sightings have value. He credits his colleague Paul Robinson for the initial detection on Jan 16th.