To put that into perspective, a microarcsecond is a millionth of an arcsecond.
Scientific American(Apr 11, 2014)
In a Feb. 17 Bad Astronomy, Phil Plait misstated the width of an arcsecond.
Slate(Feb 21, 2014)
But these are small angles, typically just fractions of an arcsecond.
BBC(Aug 21, 2013)