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  • Evaluation of Astrometric Performance at the Prime Focus of the Double-focus One-meter Telescope at the Shanghai Astronomy Museum

    Subjects: Astronomy submitted time 2024-07-03 Cooperative journals: 《天文学进展》

    Abstract: The Double-focus One-meter Telescope, located at the Wangshu Observatory of the Shanghai Astronomy Museum, is currently the largest aperture telescope dedicated to popular science in China. The telescope adopts a dual-focus design scheme that allows manual switching between the prime and Nasmyth focus. The Nasmyth focus primarily serves visual observations for popular science, while the prime focus is equipped with a scientific-grade CMOS sensor, offering a field of view of 1.5 ◦ × 1.1 ◦ . The larger field of view is suitable not only for live broadcast events but also for extensive research on various topics such as surveys of novae and supernovae, investigations of small celestial bodies in the solar system, and monitoring of artificial satellites. The astrometric precison at the prime focus of the telescope was analyzed and evaluated based on actual observation data. The results indicate that for star images with a signal-to-noise ratio greater than 5, the repeatability of measured coordinates is better than 0.1 pixel. When the signal-to-noise ratio is 30, the repeatability improves to better than 0.05 pixel. Using the high-precision Gaia DR3 catalog as the reference, the analysis reveals the presence of significant non-linear characteristics in the observation images obtained at the prime focus of the telescope. Consequently, a 3-order model (20-parameter) is necessary for data reduction. For the test observation data, the observational precision for stars brighter than 15th magnitude is approximately 0.05′′ , with the precision decreasing gradually as the magnitude becomes fainter. The observational precision for 17.5th magnitude is around 0.1′′ .