The Astrometric Performance Test of 80 cm Telescope at Yaoan Station and Precise CCD Positions of Apophis
Bifeng Guo, Q. Y. Peng, Ying Chen, Zhongjie Zheng, Yijia Shang, Dan Li, Xiao Chen
Abstract
Abstract The 80 cm azimuthal telescope has newly been mounted at Yaoan Station, Purple Mountain Observatory since 2018. The astrometric performance of the telescope is tested in the following three aspects. (a) The geometric distortion of its CCD attached. It is stable in both a single epoch and multi epochs. Eight distortion solutions are derived over about one year. The maximum values range from 0.75 to 0.79 pixel and the median values range from 0.14 to 0.16 pixel. (b) The limit magnitude of stars. About 20.5 mag (Gaia- G ) stars can be detected with Johnson- V filter exposured in 300 s. The astrometric error of about 20.5 mag stars is estimated at 0.″14 using the fitted sigmoidal function. (c) The astrometric accuracy and the precision of stacked fast-moving faint object. 24 stacked frames of the potentially hazardous asteroid (99942) Apophis were derived on 2021 April 14 and 15 (fainter than 18 mag) based on the ephemeris shifts. During data reduction, the newest Gaia EDR3 Catalog and Jet Propulsion Laboratory Horizons ephemeris are referenced as theoretical positions of stars and Apophis, respectively. Our results show that the mean ( O − C )s (observed minus computed) of Apophis are −0.″018 and 0.″020 in R.A. and decl., and the dispersions are estimated at 0.″094 and 0.″085, respectively, which show the consistency of the stacked results by Astrometrica .