Baader Planetarium 435 nm Bandpass Dark Blue Eyepiece Filter - 1.25"

Freedom from Ghost images, even when stacked. To avoid wedge errors, striae-free substrates are polished parallel to 30 seconds. First-class 7-layer hard multi-coatings on each face have 0.25% residual reflections. Baader filters are unique in this way as no other colored filter includes anti-reflection multicoatings. In addition, these coatings differ depending on the filter so that the coating performance matches the filter curve of each color. This increases transmission while decreasing reflections.

Extremely High Transmissions result in maximum contrast and isolation of planetary details, even with smaller telescopes. Efficiencies of the three longpass filters (Red, Orange, and Yellow) peaks at 98%, and efficiencies of the three bandpass filters (Green, Blue, Dark Blue) achieve 70%. 

Carefully designed spectral characteristics. Filters may be stacked without image degradation or ghosting, in order to provide even narrower passbands. Or, combine with any of the other Baader filters for interesting possibilities.

No reduction in sharpness, even at high magnifications or when using the filter far ahead of the focal plane (ie, digital imaging, or in front of a diagonal or binoviewer).