Baader 3.5 / 4nm Ultra-Narrowband Filter-Set – CMOS-optimized (H-alpha / O-III / S-II)

More Views

Images uploaded by Customers

Add Your Review with Images
Baader 3.5 / 4nm Ultra-Narrowband Filter-Set – CMOS-optimized (H-alpha / O-III / S-II)

Please choose product variant below to see price and SKU number

€ 719.00 Price excl. German VAT tax (19%): € 604.20

Please choose product variant below to see stock status  


  • Baader H-alpha / O-III / S-II Ultra-Narrowband Filter Set – Premium Grade
  • 3.5 / 4 nm FWHM (to harmonize the exposure time from H-alpha with O-III / S-II), recommended for optical systems from f/10 to f/3.5
  • For highest contrast even at strongest light pollution, minimizes star size, emphasizes finest nebula detail – indispensable under Bortle 9/8/7/(6) skies
  • Reflex-Blocker™ hard coated and planeoptically polished – with sealed coating edges (Life-Coat™)
  • Blackened edges all around, with filter-lead-side-indicator in the form of a telescope-sided black outer rim
  • Optimized for modern CMOS cameras, but likewise excellent for CCD camera technologies

We explicitly warn against observing the sun with a DeepSky 3.5 nm (equivalent to 35 Ångstroem) H-alpha narrowband filter, specialized solar chromosphere and prominence filters from SolarSpectrum start at 0.8 Ångstroem. Photographic experiments with a camera are theoretically possible, but by no means observe the sun with naked eyes – you endanger your eyesight!

* Required Fields

€ 719.00 Price excl. German VAT tax (19%): € 604.20

Product Questions

Sort by ASC
What's the actual size of your 2" filters in "mm" with and without frame/ring? What step down adapter is suggested from a 52 mm to "-- mm"?
Question by: Waqas Ahmad on Oct 10, 2016 7:54:00 PM | 1 Answer(s)
What are the threads and pitch of your 1.25" and 2" filters?
Question by: Anders G. on Sep 20, 2017 12:55:00 PM | 1 Answer(s)
What are the advantages and disadvantages of ultra-narrowband filters (3.5 / 4nm) compared to 6.5nm narrowband filters?
DSO photography from the skies Bortle 7 with refractor f7.5 and Newton f4.8
Question by: mymverger on Jul 12, 2021 1:27:00 PM | 1 Answer(s)
Hello, I have a couple of questions:
1) Will you take orders for the 65mm square versions as soon as orders open ?
2) Is there a new LRGB set that has Life-Coat and is CMOS optimised ? What is the link if so ?
I am very excited about your new filters !
Question by: Marc on Jun 21, 2021 4:58:00 PM | 1 Answer(s)
I'm thinking about adding an f/3.3 Epsilon to my stable of telescopes (I also use an f/4 and f/6 telescope). These are rated down f/3.5. I don't know that I could justify buying two sets of narrowband filters. How much would the f/0.2 difference really make? Could these still be used with good effect?
Question by: Chris on Jul 7, 2021 6:04:00 PM | 1 Answer(s)


This new generation of Baader CMOS-filters features:

CMOS-optimized Baader Filters
  • Increased contrast
  • Ever more narrow passbands
  • Reflex-Blocker coatings, for largest ever freedom from halos, even under most adverse conditions concerning aux-optics
  • FWHM on each filter category carefully designed to allow for 1:1:1 exposures, matched for typical CMOS quantum efficiency and s/n ratio
  • Identical filter thickness to existing standards, with utmost care for parfocality
  • Blackened edges all around, with filter-lead-side-indicator in the form of a black frontside outer rim, to additionally eliminate any reflection due to light falling onto the edge of a filter
  • Each filter coated individually, with sealed coating edge (NOT cut out of a larger plate with coatings left exposed, read more)
  • Life-Coat™: evermore hard coatings to enable a non-aging coating for life – even in a most adverse environment

  • Further information, test reviews, image results...

    Don´t be misled.

    These all new CMOS-optimized filters work magnificently with all existing digital camera technologies, be it CMOS or CCD. However – an owner of CCD-camera-technology will still find our previous, extremely affordable, narrowband filter technology to be fully apt for excellent imaging. But: "the Better always is enemy to the Good".

    ... can be found on our detailed Blogpost:

    Baader Blogpost:
    New CMOS-optimized Baader Filters

    Related Articles

    Additional Information

    Technical Data not yet specifiedPlease choose product variant from dropdown above to see technical data of your chosen product

    You may also be interested in the following product(s)

    Overall Average Rating:
    2 reviews
    5 star
    4 star
    3 star
    2 star
    1 star
    • Date - Newest First
    • Date - Newest First
    • Date - Latest First
    • Highest Rated
    • Lowest Rated
    • Most Helpful

    2 Item(s)

    Lemmu 189/07/2021 09/07/202117:42
    • Rating:
    Baader 3.5 / 4nm Ultra-Narrowband Filter-Set
    Excellent details showing. Crisp nebulosity, no bloated stars. Truly impressed. My 31 mm unmounted filters did'n show any edge shadowing on ASI 1600 MM. Over all highly recommended.
    • Perfomance
    • Could have telescope side indication marked on side unmounted filters (31 mm).
    Thanks for your review. With the old filters, the direction in which the filter should point to the telescope / sky was indicated by a small arrow on the side. With the new CMOS-optimized filters, the black edge itself, which only extends about 1mm into the front of the filter on one side, serves as a marker to indicate that this side should show towards the telescope. We call this the "filter front side indicator".
    Show more comments (-1) Hide comments
    NM Cosmos Observatory 341/12/2021 08/12/202118:21
    • Rating:
    Amazing contrast and tight stars!
    I just installed a set of Baader Ultra Narrowband filters on my C11 Edge. The results have been outstanding!
    • Cost, lack of halos, improved contrast
    • Nothing!
    Show more comments (-1) Hide comments

    2 Item(s)

    What kind of abuse are you reporting?
      Please, wait...