Howdy
Theers filters like the Baader Fringekiller or minus violet filters that cut out violet as well as ultraviolet, but let the rest of the spectrum throuhg, they are said to greatly help control chromatic abberations in systems that suffer it.
As for fainter blue stars in Strongmanmikes' images, they are also seen in Strikers, and in this crop of a enhanced colour saturation image I took some months ago. I believe they are known as "blue stragglers"
http://www.solstation.com/x-objects/bluestrag.htm
Scott