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 multi-night 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.