The blue/blue green light is totally blocked. The contrast between the card and the lighter zones will enormously increase. This is truly helpful when you watch Jupiter or Saturn. Or for mars, watching the poles. Starting with a telescope diameter of 10“ you can really use it effectively. What ist a color Filter for and do we really need it ? Color Filters darken the light slightly, that reaches the eye or the sensor of the camera. This eliminates for instance stronger transitions. The result is that your picture turns out with more contrast which automatically shows more details. FEATURES