  To determine the precise positions of stars in CCD frames, various centering
algorithms have been proposed for astrometry. The effective point spread
function (ePSF) and the Gaussian centering algorithms are two representative
centering algorithms. This paper compares in detail and investigates these two
centering algorithms in performing data reduction. Specifically, synthetic star
images in different conditions (i.e. profiles, fluxes, backgrounds and full
width at half maximums) are generated and processed. We find that the
difference in precision between the two algorithms is related to the profiles
of the star images. Therefore, the precision comparison results using an ideal
Gaussian-profile star image cannot be extended to other more specific
experimental scenarios. Based on the simulation results, the most appropriate
algorithm can be selected according to the image characteristics of
observations, and the loss of precision of other algorithms can be estimated.
The conclusions are verified using observations captured by the 1-m and 2.4-m
telescopes at Yunnan Observatory.
