  The limiting magnitude of the HST data set used by Cochran et al. (1995) to
detect small objects in the Kuiper belt is reevaluated, and the methods used
are described in detail. It is shown, by implanting artificial objects in the
original HST images, and re-reducing the images using our original algorithm,
that the limiting magnitude of our images (as defined by the 50% detectability
limit) is $V=28.4$. This value is statistically the same as the value found in
the original analysis. We find that $\sim50%$ of the moving Kuiper belt objects
with $V=27.9$ are detected when trailing losses are included. In the same data
in which these faint objects are detected, we find that the number of false
detections brighter than $V=28.8$ is less than one per WFPC2 image. We show
that, primarily due to a zero-point calibration error, but partly due to
inadequacies in modeling the HST'S data noise characteristics and Cochran et
al.'s reduction techniques, Brown et al. 1997 underestimate the SNR of objects
in the HST dataset by over a factor of 2, and their conclusions are therefore
invalid.
