The auto guiding system combined with sub-pixel real-time gray projection algorithm

Song Zhiming; Liu Guangqian; Qu Zhongquan

doi:10.12086/oee.2018.170586

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Song Zhiming, Liu Guangqian, Qu Zhongquan. The auto guiding system combined with sub-pixel real-time gray projection algorithm[J]. Opto-Electronic Engineering, 2018, 45(8): 170586. doi: 10.12086/oee.2018.170586

Citation:

Song Zhiming, Liu Guangqian, Qu Zhongquan. The auto guiding system combined with sub-pixel real-time gray projection algorithm[J]. Opto-Electronic Engineering, 2018, 45(8): 170586. doi: 10.12086/oee.2018.170586

The auto guiding system combined with sub-pixel real-time gray projection algorithm

1.
University of Chinese Academy of Sciences, Beijing 100049, China
2.
Yunnan Observatories, Chinese Academy of Sciences, Kunming, Yunnan 650216, China

Fund Project: Supported by National Natural Science Foundation of China, National Major Scientific Research Instrument Development Project (11527804), and National Natural Science Foundation of China, Youth Science Fund Project (11703087)

More Information

Author Bio: Song Zhiming, E-mail: szm@ynao.ac.cn

Received Date 31 October 2017

Revised Date 03 April 2018

Published Date 01 August 2018

Abstract

Abstract

Guiding systems serving modern astronomical telescopes are usually subjected to atmospheric and wind-borne disturbances that result in inaccurate calculation of the center of gravity of the guiding beacon. In order to solve this problem effectively, the sub-pixel real-time gray projection algorithm is nested into the algorithm of center of gravity of auto guiding system, which reduces the jitter of the center of gravity in a closed-loop cycle of auto guiding system without losing time resolution and achieves the goal of improving the performance of auto guiding system. First of all, in the paper, we analyze that to implement high performance auto guiding system, obtaining high real-time and small error guiding beacon's center of gravity is significant, and point out that gray projection algorithm plays an important role in the course of obtaining the guiding beacon's center of gravity. Furthermore, after analyzing the reason that classic gray projection algorithm is able to be combined with the center of gravity to increase the performance of auto guiding system, we modify the classic gray projection algorithm in the speed and accuracy so as to combine the modified algorithm with the algorithm of center of gravity of auto guiding system and achieve the goal of improving the performance of auto guiding system. Finally, we test our auto guiding system with the algorithms mentioned above in a 400 mm aperture telescope, and conclude that our system can obviously decrease the random jitter caused by wind load at the cost of less decreasing temporal resolution, and achieve the goal of improving its performance.
- auto guiding system /
- the suppression of wind load /
- sub-pixel real-time gray projection algorithm

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References

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Overview

Overview

Overview: Guiding systems serving modern astronomical telescopes are usually subjected to atmospheric and wind-borne disturbances that result in inaccurate calculation of the center of gravity of the guiding beacon. In order to solve this problem effectively, the sub-pixel real-time gray projection algorithm is nested into the algorithm of center of gravity of auto guiding system, which reduces the jitter of the center of gravity in a closed-loop cycle of auto guiding system without losing time resolution and achieves the goal of improving the performance of auto guiding system. First of all, in the paper, we indicate that the atmospheric turbulence and wind are two things that have a bad influence on the performance of auto guiding system, and then describe some existing methods used to suppress the two things. Afterwards, we have a knowledge about that to suppress the influence of the atmospheric turbulence, in a closed-loop cycle of auto guiding system, the time of calculating guiding beacon's center of gravity is significant, and to suppress the influence of wind, reducing the error of guiding beacon's center of gravity is indispensable. Therefore, we propose an efficient method that takes advantages of gray projection algorithm to calculate the displacement vector between adjacent images of auto guiding system in the time when the guiding beacon's center of gravity is computed, and then compensates the displacement vector for the center of gravity so that the influences from atmospheric turbulence and wind are suppressed, simultaneously. On the other hand, we are aware of that the performance of our method mentioned above can be further improved through rectifying three aspects of our method in algorithm. One is that making use of the structural similarity between gray projection algorithm and the algorithm of guiding beacon's center of gravity, some combinations between the two algorithms can be conducted to speed up their execution. Two is that through comparing with existing searching algorithms of minimum value of correlation function, which are an important part of gray projection algorithm, an efficient searching algorithm named as three point searching is further improved in order to obtain a promotion of computational speed of gray projection algorithm. Three is that based on the characteristic of correlation function of gray projection algorithm, an efficient fitting method in possession of a sub-pixel accuracy is applied to the correlation function so that the gray projection algorithm can obtain a sub-pixel accuracy. Finally, some experiments are conducted, and corresponding results show that our method can efficiently improve the performance of auto guiding system.