# A Voting-Based Star Identification Algorithm Using a Partitioned Star Catalog
## 5 Nighttime Stargazing Experiment  
In this section, the performance of the proposed algorithm is verified through a night-time stargazing experiment. To reduce the interference of stray light on the experiment, the observation site is selected at the Xinglong Station of the National Astronomical Observatory, Chinese Academy of Sciences, located in Xinglong County, Chengde City, Hebei Province. The geographical coordinates are 117\({}^{\circ}\)34\({}^{\prime}\)30\({}^{\prime\prime}\) E longitude, 40\({}^{\circ}\)23\({}^{\prime}\)36\({}^{\prime\prime}\) N latitude, and the site is located at an altitude of 960 m. The experiment is conducted on a clear night, and the equipment mainly includes a large-aperture telescope and a star sensor. The key parameters of the star sensor are listed in Table 1.  
As shown in Figure 12, the star sensor is fixed on the telescope, ensuring that the coaxial and star sensor are unobstructed. The telescope provides directional guidance to the star sensor based on star catalog information from the control software of the telescope. During the experiment, a celestial region is firstly selected in the star catalog from the control software, and then the telescope and star sensor are guided to point at the selected region. As shown in Figure 13, the star sensor captures a star image and the stars are identified using the star identification algorithm. \begin{table}
\begin{tabular}{c c} \hline \hline
**Parameter** & **Value** \\ \hline FOV & 15\({}^{\circ}\times 15^{\circ}\) \\ Focal length & 30 mm \\ Detection sensitivity & 6.5 Mv \\ Image plane dimension & 2048 \(\times\) 2048 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: The key parameters of the star sensor. Figure 11: Identification time with different numbers of stars. The information of the identified stars is explained in Table 2, and includes centroids, average gray value, right ascension, declination, and magnitude. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Number**} & \multicolumn{3}{c}{**Centroids**} & \multirow{2}{*}{**Average Gray Value**} & \multirow{2}{*}{**Right Ascension**} & \multirow{2}{*}{**Declination**} & \multirow{2}{*}{**Magnitude**} \\ \cline{2-2} \cline{5-6}  & **x** & & & & & \\ \hline
1 & 1240.4971 & 501.2116 & 2602.77 & 279.2346 & 38.7836 & 0.03 \\
2 & 301.2810 & 23.5686 & 1026.47 & 292.6804 & 27.9597 & 3.19 \\
3 & 762.6122 & 376.8415 & 724.18 & 284.7359 & 32.6896 & 3.22 \\
4 & 910.5179 & 1455.6426 & 820.44 & 266.6147 & 27.7207 & 3.49 \\
5 & 849.4196 & 477.9352 & 547.70 & 282.5200 & 33.3627 & 3.63 \\
6 & 918.5074 & 1262.2747 & 675.00 & 269.4412 & 29.2479 & 3.79 \\
7 & 296.6107 & 1142.7518 & 733.09 & 275.9245 & 21.7698 & 3.97 \\
8 & 74.2787 & 862.1389 & 437.67 & 281.4155 & 20.5463 & 4.24 \\
9 & 1481.8673 & 150.1228 & 1339.73 & 283.8338 & 43.9461 & 4.36 \\
10 & 90.3306 & 119.2991 & 474.42 & 292.1764 & 24.6649 & 4.61 \\
11 & 441.8809 & 1455.5560 & 468.22 & 270.3767 & 21.5958 & 4.85 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: The information of the identified stars. Figure 12: Nighttime stargazing experiment. Figure 13: Star image captured by star sensor. The numbers respectively represent the number of each star in the star image. Based on the right ascension and declination information listed in Table 2, the corresponding celestial region of the star image is captured and shown in Figure 14.  
It is pretty obvious that the relative positions of the stars in Figures 13 and 14 are virtually identical, and the right ascension, declination, and magnitude of the stars shown in Figure 14 are largely consistent with the information in Table 2, which confirms the validity of the proposed star identification algorithm. In addition, the star information in Table 2 has been sorted in the sequence of ascending magnitude. Based on this, the histogram regarding the gray value and magnitude of the stars is generated and shown in Figure 15.  
Figure 14: Corresponding celestial region of the star image. The numbers respectively represent the number of each star in the star image.