|Location of NEO 2012 QG42 at 9 pm local time on 13 September as simulated in Stellarium||Location of NEO 2012 QG42 at 9 pm local time on 14 September|
375 metre diameter Near Earth Object 2012 QG42 will be 7.4 Earth-Moon distances from us at closest approach on September 14 at 05:08 UT (that 3 am AEST, but the asteroid will still be close after astronomical twilight in Australia).
At magnitude 14 or so (ignore the Stellarium magnitudes, they are too dim) it will not be visible in binoculars or small telescopes, you will need a 6" or more scope and dark skies to see this. However, you will be able to see the asteroid visibly move over a period of a few minutes, so it's worth a look.
In Australia it's not far from the bright star Altair in Aquila, and is a good distance above the horizon at 7:30 pm local time (around astronomical twilight), and is probably too low to image by 11 pm.
Because it so so close to earth parallax is a problem, and Stellarium positions will be out. Links to detailed ephemeris's can be found here. My previous images of the asteroid are here, here and here.