Fig. 1. SNR growth curves of simulated star image adding under perfect alignment and alignment error σ₀

Fig. 2. Flowchart of the proposed method

Fig. 3. Kabsch-Umeyama algorithm

Fig. 4. Schematic diagram of bilinear interpolation

Fig. 5. Spatial error distribution of two models under different attitude transformations

Fig. 6. Relationship between deviation and attitude transformation angles for two approximation models at four typical positions

Fig. 7. Simulated single-frame star image and magnified view of faint stars

Fig. 8. Adding results using three methods

Fig. 9. Morphology comparison of partial stars before and after adding

Fig. 10. Position and morphology of faint stars after adding with three methods