centroiding

This is the problem what the center of an nbody system , or a blob in a CCD image, is.
For the nbody we have the scripts/csh/centering.sh script with results in the man page for hackdens.
For centering CCD image nothing much done, but one approach is to take the nbody from centering.sh and turn them into an image and use ccdblob/tabnllsqfit on it.