Skip to content

UPS Shipping Delays / COVID-19 Response Statement

Baader Planetarium 2" Semi-APO Filter - FSAPO-2


Baader 2" Semi APO Filter

The Baader Semi APO Filter is a truly innovative product unique to Baader Planetarium. Created by combining properties from two of their most popular filters, the Baader Planetarium Semi APO Filter is a truly effective tool for suppressing false color.

  • Baader Planetarium Semi APO Filter combines the Baader Fringe Killer coating formula with their Moon & Skyglow substrate resulting in a strong violet cut

  • Zero image degradation

  • Famous Baader quality

  • Works well as a great Mars filter

Baader's newest addition for Achromat owners. The Semi APO works like it's name implies - delivering an amazingly neutral view, while cutting most of the annoying and contrast-robbing violet fringe that plagues all achromats. The Semi-APO filter combines a stronger Fringe Killer coating formula with the Moon & Skyglow Neodymium substrate. The Semi APO filter by Baader is truly the world's most advanced "minus-violet" type filter in every regard. It's high efficiency and neutral coloration make it practically disappear in use - while making most of the violet fringe disappear! The effects on sharpness, contrast, and aesthetics are remarkable, even with small refractors. The RGB enhancement of the Neodymium substrate actually boosts color contrasts, particularly for Jupiter and Mars.

The Baader Semi APO filter has also proven to be the best Mars filter we've used - with ALL Telescopes, including large Dobsonians, SCTs, and Apochromats. The unique properties that result from the combination of the Fringe Killer's blue wavelength attenuation (attenuation - not total elimination), plus the selective Neodymium RGB passbands, result in a significant contrast enhancement of Martian features. The image retains its natural coloration, brightness, and sharpness.

The high quality of Baader Planetarium filters permits their use well ahead of the focal plane with no image degradation (for cameras or binoviewers). The high transmission and fringe reduction work great for both planetary and deep sky imaging.