The Baader Planetarium Contrast Booster Filter for 1.25" Eyepieces is much more than a simple minus-violet filter. Based on the popular Baader Moon & Skyglow filter, the Baader Contrast-Booster takes contrast enhancement and skyglow reduction to the maximum level possible from a filter. Not only does this filter deliver a significant enhancement to planetary and lunar contrasts, but it is designed to also totally eliminate the damaging blue de-focused haze present in achromatic refractors. Gone are the annoying blue halo and obscuring haze that surround and smear resolution and contrast. Subtle contrasts and colors are boosted, while displaying the full resolution your scope is capable of.The Contrast-Booster combines a special proprietary melt of Neodymium glass with a carefully designed 23-layer dielectric long-pass blocker on one face and a 7-layer ultra-low anti-reflection coating on the other face. By aggressively filtering out the defocused blue wavelengths, a light yellow tint is imparted to objects (noticeably less than a typical yellow filter).The special coatings enable over 95% transmission across key portions of the visible spectrum (including H-Alpha). This results in a filter that retains the colors and color contrasts in tough subjects like Jupiter, without excessive image dimming. Cloud bands retain their ruddy red hues, but now become more striking in contrast. The Great Red Spot finally becomes easier. Planets and Lunarscapes are set against