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Dusty farewell
Due to the proliferation of dust in the comet, it is anticipated that there will be a brightness enhancement caused by the comet being located between us and the Sun. This brightening, called “forward scatter,” could increase the brightness of the comet by as much as two magnitudes, so an impressive — albeit short-lived — surge in brightness might result from Saturday to Tuesday. 

As such, Comet McNaught’s brightness may possibly end up even rivaling the brilliant planet Venus, now currently visible in the early evening twilight sky. In addition, there is also still the possibility — albeit small — that the comet could split apart or fragment into several pieces.  Such a scenario could also make Comet McNaught appear substantially brighter. 

This weekend will also provide the last chance to catch a view of McNaught from much of the Northern Hemisphere.

But all of this will be a moot point if you can’t find the comet because trees and buildings are in your way. The prerequisite for getting a view of this spectacular comet is a very clear and completely unobstructed southwestern horizon. Also, it’s currently positioned very near to the sun against a bright twilight sky, and setting very soon after sundown. 

On Friday evening, it will be setting only about 40 minutes after the sun; on Saturday evening less than 30 minutes and by Sunday evening, just about 10 minutes. Unless the comet becomes superbrilliant by then, it may be masked by the solar glare. 

Certainly though, you should try for it on Friday and Saturday, as it can definitely be seen as a “speck” of light with the unaided eye. Through binoculars or a small telescope it shines with a golden yellow color and displays a gently curving tail of dust pointing upward.

To find it, look to the southwest shortly after sunset. Soon you’ll spot the planet Venus as a silvery-white "star" low in the sky. The comet will be positioned roughly 15 degrees below and to the right of Venus; your clenched fist held at arm’s length is equal to roughly 10 degrees, so about “one and a half fists” down and to the right of Venus is where you should find McNaught.

After this weekend, its motion southward in the sky will make it unobservable from places north of the equator.

See it with SOHO
Those who are stuck under cloud-filled skies — or skywatchers in the Southern Hemisphere who as yet cannot see the comet — can still watch for it using computers and accessing near-live images from the SOHO spacecraft.

The comet will be within range of the SOHO imagery through 16:00 UT (11 a.m. ET) Monday. It will appear to pass closest to the sun — 5.5 degrees from its center — on Sunday. 

As a bonus, the comet will also appear to pass less than 1 degree from the planet Mercury (also visible in SOHO images) on Sunday.  At 15:55 UT (10:55 a.m. ET), Mercury and the comet will be separated by only 40 arc minutes (0.67-degree).

Back in 2003 and again in 2004, the public was captivated when SOHO photographed two bright comets that — like McNaught — swept closely past the sun. Hundreds of otherwise unknown comets have actually been first detected in SOHO imagery, generating a competition among a handful of armchair astronomers. Since it was launched in 1995, SOHO officials have reported more than 1,200 comet discoveries using the spacecraft's imagery.

Heading south
Because it will appear to move rapidly southward after perihelion, Comet McNaught will quickly pass out of sight for viewers in the Northern Hemisphere, and ultimately emerging into the evening sky for observers south of the equator during the second half of January. 

Beginning Sunday, southern skywatchers should concentrate on the west-southwest horizon soon after local sunset.  Of course, binoculars will certainly enhance the view of Comet McNaught, as well as any tail that will appear to protrude up from the horizon.  As it pulls out of the evening twilight, the comet and its lengthening dust tail should be well-developed and a striking sight indeed!  A special viewers guide for Southern Hemisphere observers, can be accessed here.

Unfortunately, the comet is expected to fade quickly as it recedes from both the sun and Earth.

Trying to forecast the brightness of a new comet can always be hazardous, but the best estimate now suggests that by Jan. 21, McNaught’s brightness may subside to around magnitude zero; perhaps third magnitude by month’s end and down to fifth magnitude by early February. On this astronomer's scale, larger numbers represent dimmer objects. The brightest objects are zero of first magnitude, with superbright objects such as Venus achieving negative magnitudes.

In a recent exchange of emails, Robert McNaught revealed his feelings about his discovery.

“It is difficult for me to disentangle my passion for comets in general from the fact that I was the person to have accidentally found this specific one," McNaught told Space.com.

"I guess having my name attached to this comet must influence my excitement, but really, to be honest, it is largely an accident who finds them," he said. "Even more relevantly I am backed so expertly by an excellent team of guys at the University of Arizona who wrote the software that did the detection.” 

When asked if he has made people in his homeland of Australia aware that his spectacular namesake would soon be visible in their sky, McNaught said: “I held off till I saw just how it was going to turn out. Nothing worse than a cold turkey. They are just twigging to it now.”

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