This general purpose, Wratten #1A filter improves color saturation and balance, increases visual and photographic contrast, helps to decrease glare in lunar and planetary observing, and penetrates atmospheric haze.
Also acts as an effective dust seal; thread this filter onto the rear cell of your Schmidt-Cassegrain telescope before attaching any other accessories. The female end attaches to the rear cell of the telescope. All accessories mount onto the exterior/male threaded side of the filter housing.