Fig. 1. Flow diagram of our proposed algorithm.

Fig. 2. Comparison of thresholding results: (a) Original M42 image. (b) Otsu result. (c) Our result.

Fig. 3. Schematic diagram of the rotation invariant descriptor.

Fig. 4. Description results using our proposed star descriptor.

Fig. 5. Matching results using SIFT, SURF, and our descriptor. (a) Star detection results. (b) SIFT result. (c) SURF result. (d) Our result.

Fig. 6. Matching ratio results among SIFT, SURF, and our descriptor.

Fig. 7. Live stacking results while photographing M51. (a) No stack. (b) Three frames stacked. (c) Six frames stacked. (d) Nine frames stacked.

Fig. 8. Comparison results using ten-frames-stacked M92 images and their zoomed views. (a) Result with alignment enabled. (b) Result with alignment disabled.