The structure remains the third largest steerable telescope in the world and plays a key role in global research on pulsating stars, testing extreme physics theories including Einstein's general theory of relativity.
Cosmologists investigating the structure of the universe do not really mind which direction a telescope is pointing, since the universe is isotropic and homogeneous which is a fancy way of saying that it looks the same in all directions.
"It's correlating the increasing intensity in different bands that provides really important clues about the structure of the source, " Prof Madejski - a co-investigator on the NuStar X-ray telescope, told BBC News.