Kenko - Red Enhancer
KE035255The Kenko RED ENHANCER No.1 filter can increase saturation for all related to red colours by enhancing specific light transmission characteristics, which results in more vibrant and vivid reds. The same light transmission specifications will also filter out the yellow and orange part of the spectrum, thus reducing annoying light pollution in astrophotography.
Click here for details, specs & description on manufacturers site.