Research On FITS Image Celestial Positioning Based On WCS And General Visualization

The positioning recognition and visualization of target stars in astronomical images have important research value in astronomical observation and astrometry.This paper mainly focuses the analysis of star image,which is taken by highprecision CCD camera.Relevant algorithms have been designed and implemented,the stellar location and identification and visualization in observation star image have been developed,which support the solution of celestial location information.Based on exploring the principle of celestial location method,the requirements of star identification and visualization are analyzed,and an overall scheme including the preprocessing of star image,the positioning of stellar target and star identification,and the visualization,is designed.First of all,the preprocessing of star image is achieved via the analysis of image noise and the implement of gray correction and image enhancement.Though the analysis of image histogram,an algorithm of background segmentation based on the estimation of noise characteristics is designed,and combining with connected domain stellar target extraction is realized.By comparing the accuracy of different sub-pixel localization algorithms and combining with the characteristics of FITS image data,the sub-pixel localization of star target is realized by two-dimensional Gaussian fitting and two-dimensional Modified Moment method.Based on the analysis of the existing triangle matching algorithm,according to the actual characteristics of the system,the efficient and highly robust triangular edge matching algorithm is adopted to improve the recognition speed of stars in the observation star.Then,this paper select the WCS(World Coordinate System)theory by analyzing the algorithm of coordinate parameters recorded in the form of key/value pairs in FITS image files,establish conversion function of the image coordinate system and celestial equatorial coordinate system according to different projection methods of spherical to plane.This method can calculate WCS parameters of this conversion function to determine the image pixel and its corresponding celestial coordinates and to complete the positioning.Finally,FITS images are used to carry out scientific data transmission and analysis as a kind of mainstream data format,but its high flexibility also decides the limitation of popular science education in astronomy.Researching a general image visualization method is significant.FITS is converted to PNG or JPEG images firstly.The coordinate parameters in the FITS header are converted to metadata in the form of AVM(Astronomy Visualization Metadata),and then the metadata is added to the PNG or JPEG header.This method can meet amateur astronomers' general needs ofviewing and analyzing astronomical images under non-astronomical software platform.The overall design flow is realized through java program and tested by Aladin,WWT,picture viewer and other software.The star subdivided positioning and stellar automatic identification is realized in this paper,which have made a foundation for the celestial location system.The result is practical and referential meaning for astronomical image processing.