Check out my favorite photo of Comet McNaught taken by Jim Thorpe in Australia (hat tip to SpaceWeather.com)
It is so clear, that you can make out the two tails.
"When comets are warmed by sunlight, they spew a mixture of dust and gas into space. Instead of forming a single tail, however, the two substances drift in different directions. Dust lingers behind the comet and traces its curved orbit. Gas is pushed by the solar wind into a straight line pointing away from the sun. Comets, therefore, have two tails, the dust tail and the gas tail. (The gas tail is also known as the "ion tail.") The two tails of Comet McNaught are obvious in most photos since Jan. 22nd."