Baader Planetarium Semi-APO Telescope Filter

Item #AAS021-2

  • Your Price:
  • $147.00
  • + FREE Shipping
  • Available in 1.25" or 2" format
  • Delivers amazingly neutral views
  • Cuts annoying violet fringe
  • Amazing on Jupiter or Mars
  • High-end Baader quality
Questions? Let our experts help!
  • Description

    Baader's newest addition for Achromat owners. The Semi-APO works like its 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 result is similar performance to the Fringe Killer + Moon&Skyglow combination, but with a slightly stronger violet cut - and at an even greater $$ value.
    The Semi-APO filter benefits from all the host of world-class Baader filter attributes. The Semi-APO filter is truly the world's most advanced 'minus-violet' type filter in every regard. Its 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.


    As a side benefit, the 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 and brightness, and the optically polished surfaces maintain every bit of the image sharpness, unlike other manufacturers' filters.


    The high quality of Baader Planetarium filters permits their use well ahead of the focal plane with no image degradation (ie, for cameras or binoviewers). The inclusion of Baader's renowned UV/IR Cut coatings on the Semi-APO eliminate UV and IR wavelengths to make it ideal for high-resolution imaging with Webcams, DSLR, and CCD cameras. The high transmission and fringe reduction work great for both planetary and deep sky imaging.

    Supplier SKU


    Shipping Restrictions

    Only ships in contiguous USA.

  • Dimensions & Specifications

    Model Size

    2 Inch Semi-APO Filter


    Baader Planetarium


    2 Inches

    Telescope Accessories Series



    Color Correction Filters


    2 Year Manufacturers Warranty

  • Product Guarantee

    We stand behind all the products we sell, and your satisfaction is our top priority. If you're not satisfied with the quality of your purchase, simply send the item back to us in its original packaging within 30 days of its delivery.

    Manufacturer Warranty

    This product has a 2 year manufacturer's warranty against defects is provided. If you have specific questions about this product's warranty please contact Alpine Astronomical's Customer Service department by email at

    Return & Exchange Policy

    At our site, returns are easy! You may return new, unused, and resalable items for a refund or exchange. Simply ensure that the item is returned in its original product packaging within 30 days of delivery.

Ask The Experts

Have questions about an item or need advice on selecting the right astronomy gear? Our team of telescope experts is here to help! Avid amateur astronomers themselves, they've tested products in the field and can provide personalized recommendations.

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