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

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

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

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Which side should face the telescope?
  • 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/3.4
  • 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!

Baader Narrowband-/Highspeed Filter Selector

To make it easy for you in the future to decide which kind of Highspeed (or Narrowband) filter you need for your telescope, please check our Filter-Selector, that provides you the correct individual graph based on your entriest, in which you can find the perfect filter for your telescope by f/ration and central obstruction.

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

Product Questions and Answers

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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)

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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)

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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)

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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)

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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)

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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

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    4 Item(s)

    Francesco di Biase 322/11/2021 19/11/202108:15
    • Rating:
    Baader Ultra Narrowband filter unter the sky
    My general opinion on performance, supported by the tests carried out and my experience with other high-end products, is fully positive. I believe that they can be equated with the most famous brands, with the advantage of a cheaper price.

    Of course, as soon as I need them, I will seriously consider using these filters for my setup.

    Attached the final result of my tests.
    Mr. Fransceco di Biase had the opportunity to test the new Baader Ultra Narrowband Filters 36mm in unmounted version in his small observatory with a sliding roof under a suburban sky (19.40 SQM) and he sent us a detailed field report. We are very pleased about the positive feedback on the new CMOS-optimized Baader 3.5 / 4nm Ultra-Narrowband Filter.

    Please read here the detailed test report of Franseco di Base from 06 November 2021: Baader Ultra Narrowband Filters Under The Sky
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    Bob J 297/10/2021 25/10/202122:33
    • Rating:
    3.5nm Ha Ultra Narrowband CMOS Optimized
    I have only got to image with the Ha filter to any extent. I am using a ZWO ASI 294MM P. It is set up in a dual rig with the exact OTA and imaging train. I have the new CMOS filters in one wheel and the older version of the Ultra Narrowband in the other. The contrast was noticeably improved with the CMOS filter. I just got to start using the SII and as quick comparison, I had almost no data present on a 900 sec image of the Heart Nebula. On the other hand, with the new CMOS SII I had lots of data with the same exposure time. I sold!!! So much I just received my second set today for the other filter wheel. By the way this was imaged under a 98% Full Moon. Almost directly in my targets line of sight. 44x900s for 11 hours!
    • High Contrast!
    • Should be an indicator for the direction to install with the 1.25" Cell
    Thanks for your review! Regarding the indicator for 1.25" filters:

    Traditionally 1.25" filter cells were meant to thread onto an eyepiece. For this reason it is almost regarded common knowledge which side of the filter needs to point towards the telescope.
    It is quite rare that there is a provision at all to thread a filter in reverse order. For this reason we are glad to take this opportunity to point out, that its always best to mount a filter cell in the way, which is commonly acknowledged.

    For manufacturers of accessories that allow the customer to mount the filter cell in reverse direction, it might be in order to also remind them to inform their customers, that this way of mounting a filter may result in the filter being installed in reverse.

    For skilled users certainly it would be possible to flip the filter in the cell if needed (by removing the retainer ring that holds the filter in its cell – as we deliberately do not tighten these retainer rings with force). More information why our filters may "clatter" also here:
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    Lemmu 189/07/2021 09/07/202117:42
    • more than 2 year(s)
    • 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".
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    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!
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