ORIGINAL: Len in Maryland
Sometimes it's best to put a piece of white paper behind the object being viewed. Having this sort of background will aid in seeing any variances.
I do something like this. I take 3x5 index cards,with blue lines on them, and put one under each end of the arrow when I spin it. I line up the shaft with one of the lines and then spin and that gives me a very good visual concerning the straightness on each end.