With the aid of a star test (or sector-star test) exposure, the size and shape of tube assembly focal spots can be determined in a very simple manner. This method is less complicated than the pinhole or slit camera process and assuming an approximately ideal intensity distribution in the focal spot, it is in many cases fully adequate.

Further information on the topic "Determining the focal spot through star test" is summarized here. This information can also help you to find the right test type for your field of application.