The image shows the expected track of comet McNaught through SOHO's coronagraph LASCO C3. The comet will appear in the field of view of C3 at around 11:00 CET (10:00 UT) on 12 January 2007 (a few hours before perihelion) in the upper-left of the images and travel almost vertically down, exiting C3's field of view in the lower left at roughly 03:00UT on January 16th.
Recent estimates of the comet's maximal brightness have ranged widely from magnitude +2.1 (about as bright as Polaris, the North Star) to a super-bright -8.8 (about 40 times brighter than Venus)! The lower the magnitude number, the brighter the object. The brightest stars in the sky are categorized as zero or first magnitude. Negative magnitudes are reserved for the most brilliant objects: the brightest star is Sirius (-1.4); the full Moon is -12.7; the Sun is -26.7.
Current estimates put comet McNaught at magnitude 0 to -1, and it is still brightening. It could be -2 or -3 by the time it reaches LASCO's field of view. This means it will be brighter than comet NEAT or comet 96P/Machholz. In other words, this could be the brightest and most spectacular comet that SOHO has ever seen!