A new comet was discovered by Rob H. McNaugt (Siding Spring Survey) on July 28, 2008. The cometary nature of the magnitude 17.5 object was confirmed by later observations. With this discovery, Rob McNaught has now 43 comets to his credit. The preliminary orbital elements of the comet C/2008 O2 (McNaught) indicate a perihelion passage on November 13, 2009 at a distance of 1.3 AU from the Sun. The comet should reach magnitude 7.4 at the time of the closest passage to the Sun.