For the CCD serial star images

while the space target is moving

the background is still moving because the CCD flat is moving. The global movement of background stars and the local movement of the space target both exist in the star-sky images

which add difficulty to dim target detection. In order to detect dim space target with high efficiency

a star-sky image registration algorithm is put forward. First is the pretreatment

including radiation asymmetry rectification and stray-light rectification. Then

for each frame of image

centroids of the brightest stars are computed. The stars which can radiate in every frame are used as control points to compute the global motion parameters. Finally

the star-sky image is transformed into a form of star centroid coordinate matrix. And the background stars can be eliminated by using the global motion parameters. The algorithm omits image resampling and transformation steps

and thus saves abundant of computing time. The registration image can eliminate the background stars and the dim target can be easily detected from the registration images.