Baader Planetarium Filters

Durable dielectric coatings for a lifetime of service. Plane-parallel polished substrates for the highest level of optical performance. Precise glass thickness of 2 mm for 1.25" and 2" mounted filters, and 3 mm for 50.8 mm round unmounted filters to make the filters par-focal within each respective size for imaging applications.

Nebula Filters
  • Visual Narrowband O-III Filter 1.25" (BPO3125) and 2" (BPO32)
  • UHC-S High Transmission Nebula Filter 1.25" (BPUHCS125) and 2" (BPUHCS2)

  • Colored and Contrast Filters
  • Colored Filters 1.25" (BPCF125) and 2" (BPCF2)
  • Contrast-Booster Filter 1.25" (BPCB125) and 2" (BPCB2)
  • Neodymium ("Moonglow & Skyglow") Filter 1.25" (BPMS125) and 2" (BPMS2)

  • Filters for Lunar / Solar Studies
  • 2" Neutral Density 1.8 Filter (BPND18)
  • Polarizing Filter 1.25" (BPPOL125) and 2" (BPPOL2)
  • Solar Continuum Filter 1.25" (BPSC125) and 2" (BPSC2)

  • CCD/Webcam Imaging Filters
  • U-Filter (Venus-Filter) 2" (BPU2)
  • UV-IR Rejection Filter 1.25" (BPUVIR125) and 2" (BPUVIR2)
  • Visual Narrowband O-III Filter - 1.25" (BPO3125) and 2" (BPO32)

    The non plus ultra for visual deep-sky observers, especially under extremely light-polluted skies. See planetary nebulae and supernova remnants come alive with the enhanced contrast from these filters.

    Among the narrowest transmission band O-III filters on the market, ideally suited for both visual use and for many imaging applications thanks to its unsurpassed contrast. No image degradation is perceptible even at the highest magnifications. Features the same ultra-hard, extremely durable vacuum-deposited dielectric coatings employed on the UHC-S filter.

    The Baader Visual O-III Filter effectively blocks the entire visual spectrum with the exception of the two closely paired emission lines from doubly ionized oxygen, eliminating the annoying colored halos surrounding stars that often appear through O-III filters manufactured by means of less sophisticated coating technology. We also offer two additional versions of this filter with extended infra-red blockage for many of today's IR sensitive CCD chips - in a 2" mounted and in a 50.8 mm unmounted configuration for the STL series of cameras.

    Transmission Curve - PDF document
    Extended Transmission Curve

    UHC-S High Transmission Nebula Filter - 1.25" (BPUHCS125) and 2" (BPUHCS2)

    A new generation of light pollution rejection/nebula filter. Baader Planetarium's unique “golden mean" design transmits sufficient light for even small aperture telescopes while preserving the high contrast of traditional UHC (Ultra High Contrast") filters.

    Exactly tailored to block off all of the common streetlight emissions. The sensible alternative to all previous generations of Deep Sky and UHC filters both visually and photographically.

    Transmission Curve - PDF document
    Extended Transmission Curve

    Color Filters - 1.25" (BPCF125) and 2" (BPCF2)

    These color filters provide the highest levels of image brightness and freedom from scattered light, combined with uncompromising image sharpness at the high magnifications required to observe delicate planetary details.

    All surfaces are polished to exacting tolerances of flatness and parallelism to far surpass the performance of "flame-polished" substrates employed in typical economy filters. All surfaces feature 7-layer multi-coatings that reduce reflective losses to a mere 0.25%.

    More Information
    Transmission Curve - PDF document
    Extended Transmission Curve

    Contrast-Booster Filter - 1.25" (BPCB125) and 2" (BPCB2)

    The ultimate contrast filter for all refractive optical systems. Eliminates color error of achromatic doublet objectives to provide the highest level of definition while correcting color balance. Surface details on the Moon and planets stand out boldly.

    You haven't really seen Jupiter's Great Red Spot though your achromatic refractor until you've used this filter.

    More Information - PDF document
    Transmission Curve - PDF document
    Extended Transmission Curve

    Neodymium ("Moonglow & Skyglow") Filter - 1.25" (BPMS125) and 2" (BPMS2)

    The Super Contrast Filter for all REFLECTOR and APO-TELESCOPES.

    This filter was designed to transmit the maximum amount of incoming light, while suppressing skyglow due to artificial lighting and background glow when the Moon is up. The filter material is a special Neodymium glass that effectively filters out selective wavelengths of low-pressure sodium and other manmade sources. Please note that this is NOT a moon filter, although it will enhance contrast in views of the moon. To dim the moon to a comfortable viewing brightness we recommend a neutral density filter which can be used to greater effect when combined with this Neodymium filter.

    More Information
    Transmission Curve - PDF document
    Extended Transmission Curve

    Neutral Density 1.8 Filter - 2" (BPND18)

    This 2" filter is threaded for 48 mm metric threads. It has a transmission rate of 1.6%, making it an ideal moon filter for large aperture instruments. Use this filter with the AstroSolar Density 3.8 Film for safe solar observation.

    IMPORTANT! Do not attempt to use this filter without a white-light filter in front of your main telescope optics. While it will supplement the ND 3.8 Photographic Density filter material to yield a safe combined transmission level, it is wholly insufficient by itself for solar viewing. Serious damage to your eyes could result from improper use of solar filters!

    Polarizing Filter - 1.25" (BPPOL125) and 2" (BPPOL2)

    A polarizing filter is an excellent filter choice for lunar viewing. It provides variable neutral density (it darkens or lightens) as it is rotated, accomodating the different lunar stages. This filter is a single stage polarizing filter and must be used with a diagonal mirror, such as our MaxBright Diagonal (PMDMAX), to achieve the polarizing affect. This polarizer can similarly be used with the Herschel Prism (BPHERP) for solar viewing, but must always be used in addition to the ND3.0 filter (the ND3.0 filter must always remain in the Herschel Prism for viewing safety). When either lunar or solar viewing, the filter can be screwed onto the barrel of a 2" eyepiece or onto our 1.25" Eyepiece Adapter (ADA125). Note that in the case of our ADA125, you may need to add our 2" Barrel Extension (A3703) to accomodate 1.25" eyepieces with extra long barrels.

    Solar Continuum Filter - 1.25" (BPSC125) and 2" (BPSC2)

    Unsurpassed contrast of photospheric details is achieved by an extremely narrow half bandwidth of only 8nm. Functions like a monochrometer, suppressing the effects of atmospheric turbulence to provide images that appear markedly more stable.

    Focus "Sweet Spot Generator" - completely eliminates the usual focusing guesswork - the image snaps to a razor sharp focus at the exact focal position. Image the sun the way professionals do!

    VERY IMPORTANT: The Solar Continuum Filter MUST be used in conjunction with a visual density white-light solar filter or Herschel Prism (with ND3.0 filter) in front of the lens. We suggest Astro-Solar ND 5.0 Visual Filter material, also from Baader Planetarium. If you prefer a ready-made filter, we suggest the Baader Planetarium ASSF, ASTF or ASBP solar filters or Kendrick solar filters, also constructed with AstroSolar Safety Film. DO NOT attempt to use this filter without a white-light filter in front of your main telescope optics. Serious damage to your eyes could result.

    Transmission Curve - PDF document
    Extended Transmission Curve

    U-Filter (Venus-Filter) - 2" (BPU2)

    The Baader Venus filter blocks the entire spectral region from 200nm to 1500nm except for a very narrow bandwidth from 300nm to 400nm in the far violet. Transmission efficiency reaches 80% at the peak. This filter makes it possible to image cloud detail on the surface of Venus.

    Please Note: The Baader U-Filter is specifically for digital imaging (digital SLR, webcam or CCD). Since visual perception stops at about 400nm (380nm if you're lucky), the light transmitted through the filter is not detectable by the human eye. Do not purchase this filter for visual use! Also note that the colors in the photo at left are the true reflected colors of each side of the filter and are the result of the different dielectric coatings used on each surface.

    The accompanying photograph of Venus, taken by M. Rietze just 2 days before transit, shows the cusps enclosing two-thirds of the planet's circumference.

    Extended Transmission Curve

    UV-IR Rejection Filter - 1.25" (BPUVIR125) and 2" (BPUVIR2)

    This filter is a must for all digital imaging with CCD cameras, digital cameras and webcams. Corresponds to the L ("Luminance") filter in an RGB filter set. Provides pinpoint stellar images.

    Reflects deleterious infrared rays without heating, while providing 98% transmission over the entire visual spectrum. The plane-parallel polished substrate allows this filter to be employed at large distances from the focal plane, notably in binocular viewers and for eyepiece projection.

    Exciting possibilities in combination with other filters! For example, when combined with the Solar Continuum Filter, the entire accessible electromagnetic spectrum is blocked with the exception of a narrow region around 540nm.

    More Information - PDF document
    Transmission Curve - PDF document

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    This page was last modified: June 4, 2018

    Astro-Physics, Inc.
    11250 Forest Hills Road, Machesney Park, IL  61115, U.S.A.
    Phone: 815-282-1513   Fax: 815-282-9847