Research Of Image Acquisition And Rocessing Technoloy Of High Sensitivity Astronomical CCD Camera

The development of deep sky photography makes astronomy enthusiasts require higher performance photography tools. The performance of astronomy CCD camera, which is one of the most important tools of deep sky photography, directly determines the quality level of photography. This thesis aims at developing application software of high-sensitivity astronomical CCD camera, and focuses on the research of the image acquisition and image processing technology.According to the using demand of the high-sensitivity astronomical CCD camera, the composition of astronomical CCD camera system is introduced. Moreover, the software system of the astronomical CCD camera has been designed, which includes the basic functions such as image capture and display, exposure control, temperature control, image stretching, etc. Furthermore, the automatic star tracking algorithms in deep sky photography and uneven background correction algorithm have been analyzed to find out a suitable solution to improve the software system.Due to the movement of the asterisms caused by the rotation of the earth, many pieces of string would occur in the celestial image formed after a long exposure time in deep sky photography. In order to track the star points in real time so that the star points will locate the field of view all the time, automatic guiding system is used to calculate the star position and control the equatorial instrument program module. The basic principles of automatic guider are introduced in detail, which include the proper star selection and tracking algorithm. Considering that the star energy distribution in the image is approximately Gaussian distribution, a reliable target star selection method is proposed. The algorithm analyzes a threshold value of the image firstly, and then a number of candidate stars are detected according to the threshold condition. The target star is selected from the candidate stars by guiding criterion. Finally the centroid coordinate of the target star is calculated through Gaussian fitting. The accuracy of the target star detection and calculating efficiency are both improved. The experimental results show that the proposed algorithm can achieve a good automatic guiding performance.Based upon the causes of uneven background, as well as the comparison among the existing uneven background correction methods, a new one which is suitable for our system is proposed. Firstly, apply the algorithm to the original image filter to eliminate the interference of salt and pepper noise. Then extract the uneven background image by mathematical morphological opening operation. Afterwards, obtain the correction template by normalized the background image. At last, acquire the final correction image by dividing the gray level of each pixel in the original image to the corresponding location value in the correction template. The experimental results show that the algorithm has great effect on uneven background correction. Besides, the algorithm is stabilized, which is applicable to different uneven background images caused by the CCD camera.