My photo of comet McNaught taken 23rd Jan 2007, Olympus E330, 60sec, ISO400, Zuiko 50mm f/1.4 lens at F/2 in rural region
see HERE for more of my photos and info on comet McNaught P1
The new designation system gives the year of discovery followed by a letter, indicating the half-month in which it was discovered, and a number, indicating number of the discovery within the half-month. So C/1998 A2 would indicate the second comet discovered in the first half of January 1998. In the case of Comet Halley, the 1P indicates that it is the first numbered periodic comet. (There are well over 100 numbered periodic comets at the present time.)
The old-style system gave the year of perihelion passage and the Roman numeral specified the order of perihelion passage during that year. Hence, 1970 II was the second comet to pass perihelion in 1970.
Recent brighter comets: