A Practical Method for Improving an Asteroid’s Astrometric Measurement

Abstract We present a method for obtaining high-precision asteroid astrometry from a ground-based optical telescope. While the observation of a faint asteroid often employs a single clear filter to ensure a high signal-to-noise ratio, this strategy introduces strong differential chromatic refraction (DCR). We demonstrate our method based on a sample of 16 asteroids observed via a single clear filter, performing data reduction with a newly published DCR calibration model. The approach employs multinight observations to derive the asteroid’s color index (CI) and correct its positional residuals after a suitable plate-constant model solution. For the full sample, the standard deviations of residuals relative to the Jet Propulsion Laboratory ephemeris were reduced to approximately 0 . ″ 02 in each direction. This precision represents an improvement of approximately 1 order of magnitude over the astrometric precision typically achieved by major surveys. Furthermore, the derived CIs show general consistency with previous photometric records. Our method provides a robust calibration strategy for future surveys, enabling high-sensitivity broadband observations to achieve high astrometric precision.