Astrometric Observations of NEA 1998 HH49 Using the Daocheng 50 cm Telescope

Abstract

This study details an astrometric observation campaign of the NearEarth Asteroid(NEA) 1998 HH49, conducted with the aim of reffning our understanding of its physical characteristics. Utilizing the 50cm telescope located at the Wumingshan Mountain in Daocheng, Sichuan, images were obtained over four nights, from October 19 to October 22, 2023. These observations were processed
using Astrometrica software, facilitating the precise determination of the asteroid’s position.The observational results were compared with the ephemerides from three distinct sources to verify accuracy: the Jet Propulsion Laboratory (JPL) Horizons System, the Institut de Mécanique Céleste et de Calcul des Éphémérides(IMCCE) Miriade, and the Near-Earth Objects Dynamic Site (NEODyS-2). When compared with the JPL ephemeris, it yielded a mean observed-minus-calculated (O-C) result of 0.07'' in the Right Ascension (RA) direction and -0.35'' in the Declination (Dec) direction. Furthermore, the comparison with the IMCCE ephemeris yielded the mean O-C results of 0.08'' in the RA direction and -0.06'' in the Dec direction. The comparison with the NEODyS-2 ephemeris yielded the mean O-C results of 0.08'' in RA and -0.49'' in Dec direction. The study's findings demonstrate a general consistency between the observed data and the ephemeris predictions, with minor discrepancies observed across the datasets. Notably, both the JPL and NEODyS-2 ephemeris show that the residuals in the Dec direction exceed those in the RA direction. The disparities may result from atmospheric differential color refraction, ephemeris discrepancies, observational errors, and other factors. Additionally, it's worth noting that further investigation is required due to the potential influence of additional factors. Overall, the Daocheng 50cm Telescope exhibits the ability to conduct high-precision positional measurements.