Near Earth Asteroid (3122) Florence passes Earth during the evening of Friday 01 September 2017. The 4.3-km wide asteroid passes Earth just over 18 times further away than the Moon. While that is a very comfortable miss, and there is no likelihood of it hitting the Earth in the next few centuries, this is the closest pass of such a large Near-Earth Asteroid since the first one, Eros, was discovered in 1898. And it wont be back for another close pass until 2057.
For Australian locations it will be high in the northern sky between the constellations of Aquarius and Aquila It passes closest to Earth at about 10:06pm AEST on 01 Sep when it will be around 9th magnitude. So it will be visible in good binoculars and small telescopes (but not to the naked eye)…if you know exactly where to look!
If you are using binoculars these finding charts by Astroblogger will help you find it. If you have a computerised telescope set it up as accurately as you can before searching for asteroid (or minor planet) ‘3122 Florence’. You may need to download its orbital information for your software. And be patient, the asteroid is moving across the sky slowly, it may take a few minutes to detect any motion.
If you don’t have fancy equipment or have trouble with the maps then you can watch it online at either Bareket observatory or The Virtual Telescope Project. If its cloudy on 01 Sep it will still be visible for a few more nights before getting too faint and too close to the northern horizon.