Attached Link: http://www.edb.utexas.edu/teachnet/QTVR/NodalPoint.htm

Ok,   this is a short site telling what "nodal piont" is....might be helpful.  It was to me. Never entered my thoughts about that being the rotational center..even with some physics background. Makes perfect sense.   Goood tips here on this thread, folks. Thanks.         TomDart.