Baader Dark Blue 435nm Bandpass Filter - 1.25" Round Mounted

Baader Dark Blue 435nm Bandpass Filter - 1.25" Round Mounted
Item # BA-FCFDB-1
  • This Baader Dark Blue Filter has a bandpass at 435nm and is designed for 1.25" eyepieces.
  • Substrates are plane-parallel polished to within 30 seconds of arc.
  • The Baader Planetarium Dark Blue Filter 70% transmission efficiency and is perfect for revealing lunar details, bright comet tails and planetary work.
  • Can be placed anywhere in the optical path without introducing astigmatism or other defects.


Baader Dark Blue 435nm Bandpass Filter - 1.25"

Baader Planetarium astronomy filters by far supersede the mediocre quality of common "flame polished" color filters. A fine optical polish and 2 mm thick glass allows these filters to be inserted anywhere into the optical path without introducing astigmatism or other defects. For instance, they can be used in front of a binocular viewer without degrading the image in any way. Substrates are free of striae and plane-parallel polished to within 30 seconds of arc. This eliminates any double images or ghosting due to wedge errors in the glass.

The filter cell features the largest clear aperture of any telescope filter on the market for complete freedom from vignetting at any focal length. The front "crown" incorporates milled notches, which makes handling and threading the filter an easy operation in the dark. All surfaces are treated with a 7-layer Multi-Coating, featuring a mere 0.25% residual reflection. It is the most elaborate coating ever applied onto amateur color filters, resulting in a filter free of any false reflections under any incident angle of light. Light is the hottest commodity for all planetary observation. Especially during high magnification work, whether you have enough light or not is the deciding factor for the recognition of the subtlest planetary surface detail, much more important than a horde of different filters of mediocre execution. Less is more: 7-layer MC-coatings not only provide a brighter image, they prevent the softening effect of scattered light! Scattered light kills exactly those subtle features in planetary detail that you are longing to see. Painstaking attention to coatings and perfect optical figuring are simple reasons why the image contrast through these premium filters is so rock-solid.

Baader Planetarium Dark Blue 435nm Bandpass Filter Features.

  • Freedom from ghost images, even when stacked.
  • Striae-free substrates are polished parallel to within 30 seconds of arc to avoid wedge errors.
  • Finest 7-layer hard multi-coatings on both faces feature 0.25% residual reflections (Baader filters are unique, no other colored filter incorporates anti-reflection multi-coatings).
  • Extremely high transmission results 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).
  • With the 2" size, only one filter is needed for binoviewing. Only Baader colored filters have the optical quality necessary for use this far ahead of the focal plane.
Additional Information

Additional Information

Manufacturer Baader
Type of Filter Color
Filter Usage Imaging, Visual
Single or Set? Single Filter
Filter Size 1.25"
Filter Shape Round
Filter Mounted? Mounted
Warranty 1 Year Warranty
Peak Transmission 70%
FWHM Bandwidth 435nm
Filter Kit Contents Dark Blue

Customer Reviews 1 item(s)

Ronnie, NT5B
Greatly enhances resolution at higher magnifications (280x for bright objects by reducing fringe glare, giving a finely detailed image in the 435nm (blue end of the spectrum. Great for Copernicus crater & high detail lunar features. Has a definite WOW factor that will cure any eye strain searching for those fraction of an arcsecond details wanted in high resolution lens systems. For viewing through a 1.25 eyepiece using a more moderate magnification (80x with a wide field of view (70 degree apparent fov, you will have an experience of the Moon unobtainable in any CCD imaging camera, not able to mimic with photos.
The Baader Planetarium's Premium Color 435nm (Blue Bandpass Filter, with the easy finger grip barrel threaded male on one side, and female on the other is stackable, but works with surprising clarity as a stand alone filter. The high definition advanced coatings eliminate ghost images using optical polished flats and extreme optical quality.
This would probably be one of your most favorite lunar filters for clear viewing, and visitors will be awed by the Blue Moon.
1= Houston, We Have a Problem & 5= It's Out of This World
Review by StationNT5Bmedia / (Posted on 11/1/2009)
Included Items

Included Items

  • Baader Dark Blue 435nm Bandpass Filter - 1.25"
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