The bus sized asteroid 2012BX34 made a close approach to Earth last night , cominfg within less then 0.2LD to Earth .  
If you were an observer following Earth at ca. 0.15 LD ( trailing ) would you be able to predict the asteroid would be at a near collision course with Earth ?  
 
The animation hereunder starts about 100 days in the past and looks at Earth from a trailing point at 45.000 kms .  
The asteroid appears soon after the start of the animation at the high left in yellow . It then moves smoothly to the right , but then suddenly seems to turn its back ...
The field of view is 145°.  
One frame last for 1.8 days . Time step was 2 hours .  
The moon appears as the silvery line moving from right to left .  
As the viewpoint is within the moons orbit ( 45.000 kms from Earth ) the moon passes behind the camera , so we can only see part of its orbit here.  
In order to focus on the asteroid the apperent size of the asteroid was magnified by more than 10000 times.