Naked Eye Appearance:
Seeing a comet with the naked eye is a somewhat rare occurrence
. On the average we get a naked-eye comet once every five or six years and this includes comets that become barely visible to the naked eye. Classic comets with long tails only appear about once every 10-12 years. The motion is very difficult to detect and comparing its place with naked-eye stars over several days is the only way to see it move. In general, comets are best observed with telescopes or binoculars.
What are They?
Comets are primarily composed of ice and dust, causing some astronomers to refer to them as "dirty snowballs." They typically move through the solar system in orbits ranging from a few years to several hundred thousand years. Comets are not on fire. As they near the sun, the sun's heat melts the comet's ices and releases dust particles which are most evident as the comet's tail. Comets rarely come within a few million miles of Earth and, thus, have a slow apparent motion across our sky. Typical comets remain visible for periods of several weeks up to several months.
Example #1: This movie of C/1997 T1 (Utsunomiya) was obtained by Tim Puckett on 1997 October 7. It was obtained with a 60-cm reflector and shows the comet's motion over a period of about 75 minutes. The field of view is 9 x 9 arc minutes or about one-third the diameter of the full moon.
Example #2: This movie of C/1995 O1 (Hale-Bopp) was obtained by Tim Puckett on 1997 March 5. It was obtained with a 30-cm reflector and shows the comet's motion over a period of 66 minutes. The field of view is 22 x 22 arcmin or about three quarters of the diameter of the full moon.
Example #3: This movie of C/1994 N1 (Nakamura-Nishimura-Machholz) was obtained by Dennis Luse and Willia ...