The Implementation Of Astronomical Guiding Application And Its Algorithms On PC

Astronomical observation for a long time has required higher pointing and tracking accuracies of the telescope,so the astronomical star guiding has become an essential work.The astronomical star guiding software is a very important part of astronomical star guiding system to realize the closed-loop control.its performance directly affects the precision of astronomical observation.Our purpose is to develop a stable and reliable astronomical star guiding software running on PC.We have analyzed the various components of the astronomical star guiding system in this paper.Based on the work done by the astronomical star guiding software,we have designed its overall structure,divided it into six functional modules which are image acquisition,image preprocessing,guide star selection,guiding control,telescope control and status monitoring.and written code to achieve one by one.In the design of hardware and software interface of the astronomical star guiding software,we have achieved the independence of the equipment on the base of the ASCOM standard,and improved the compatibility of the software.In the design of the overall structure of the astronomical star guiding software,we have adopted MVC(Model-View-Controller)mode,which realizes the isolation of data processing and user interface,and improved the portability of the software.After analyzing all kinds of noise sources of astronomical image,we are not limited to the basic image preprocessing algorithm,but add more targeted dark field processing and bad pixels processing in the astronomical star guiding software to protect the original image data while removing noises.It is more conducive to the subsequent star subdivision location.We have adopted the threshold centroid algorithm on the base of the gray-level to locate the sub-pixel position of star point in the software.This method is fast and accurate,and it is suitable for astronomical star guiding software with high real-time requirement.At the same time,we make a reasonable estimation of the brightness and signal-to-noise ratio of star point.According to the brightness,signal-to-noise ratio and the distance from star point to image center,we design and implement the automatic star selection algorithm.We designed a reasonable method of displacement calibration in the software to determine the mapping relationship between the equatorial coordinates and the image coordinates.We use the calibration results to convert the real-time detection of the guide star offset to the equatorial coordinates,then through the star guiding algorithm to calculate the actual correction required,and output the star signal to control telescope.So,the closed-loop control of the whole astronomical star guiding system is realized.Finally,through the actual operation of the astronomical star guiding software,we have done star guiding experiments,reached predetermined star guiding function,and further verify the rationality of the overall design of the astronomical star guiding software and the correctness of the code.