[Chimera-users] How to determine the distance from SG of Cys to the centroid of a nearby Trp ring

I am using Tools/Structure Analysis/Axes -Planes-Centroids. Selecting the Trp Indole ring, obtaining the centroid. Then selecting SG of Cys and the centroid and drawing an axis. That axis does not seem to pass (exactly) through the SG and Centroid- that' my first problem, the 2nd problem is to get the distance between the centroid and SG.