Seen here on June 13th from southern New Mexico, this Comet McNaught's long ion tail sweeps across the telescopic field of view (a negative image is inset).

Remarkably, the ion tail easily stretches past background star cluster NGC 1245 (upper left) in the constellation Perseus, about 1.5 degrees from the comet's lovely greenish head or coma.

Radiation from the sun pushes dust particles away from the coma, forming a dust tail, while charged particles from the sun convert some of the comet's gases into ions, forming an ion tail.