In highly dynamic environments

there can be motion blur on the star images taken by star sensors

which will seriously affect the star spot extraction accuracy. Regarding to such issues

a method is proposed in this paper to directly extract star spots form motion blurred star images assisted by prior information. First

the prior attitude information of inertial navigation systems and star sensors was utilized to predict the coarse star spot coordinates on the motion blurred star image

which were regarded as seed points for local region growth to obtain the range of the star spots. Then

the star spot motion trajectory was estimated based on the angular velocity output of the inertial navigation system

and star spot coordinates were calculated by the centroid method. Finally

errors of the star spot coordinates were corrected according to the relationship between the star spot motion trajectory and the centroid extraction error. Simulation results show that compared with the method that extracts star spots after restoring the motion blurred star image

the proposed method can ensure high accuracy of star spot extraction and good anti-noise performance under highly dynamic environments. Besides

the proposed method can greatly reduce the processing time for motion blurred star images

which is helpful to ensure that the data update rate of star sensors is not greatly affected by highly dynamic environments.