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Filters

A filter decides what light reaches your sensor or your eye, and under Canadian suburban skies that decision often matters more than aperture. The right narrowband filter can make a nebula imageable from a driveway that visually shows almost nothing. David Astro carries filters in Canada — narrowband, LRGB, light pollution, planetary, solar and scientific — in 1.25", 2", 31 mm, 36 mm and unmounted formats, shipped from Canadian stock.

Filter selection is where our team spends a lot of time, because bandwidth, f-ratio and sensor size interact in ways that are not obvious from a product page. Tell us your telescope and camera and we will recommend a set that works together.

Filters

CA$1,678.00 - CA$1,678.00
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Askar 3nm Colour Magic Ha/OIII & SII/OIII (E1+E2) Filter Package

ASK-CM-E1E2
1 in stock

Enables SHO "Hubble Palette" imaging with a one-shot-color (OSC) camera Includes two 3nm dual-bandpass filters: E1 (Hα+OIII) and E2 (SII+OIII) Iso...

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CA$1,678.00 - CA$1,678.00
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CA$847.00 - CA$847.00
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Askar 3nm Colour Magic Ultra Ha/OIII E1 Filter - 2"

ASK-ASKAR2DBE1
1 in stock

Dual-bandpass for Hydrogen-alpha (656.6nm) and Oxygen-III (500.7nm) Ultra-narrow 3.7nm (Ha) and 4.0nm (OIII) FWHM bandwidths 85% peak transmittanc...

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Askar 3nm Colour Magic Ultra OIII/SII E2 Filter - 2"

ASK-ASKAR2DBE2
1 in stock

Dual-bandpass design captures OIII (500.7nm) and SII (672nm) simultaneously Narrow 3.7nm (OIII) and 4.0nm (SII) FWHM for high-contrast imaging Pea...

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CA$875.00 - CA$875.00
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Askar 6nm Colour Magic Ha/OIII & SII/OIII (D1+D2) Filter Package

ASK-CM-D1D2
3 in stock

6nm Dual-Bandpass Filter Set Includes D1 (Hα+OIII) and D2 (SII+OIII) Filters Enables SHO-like imaging with color cameras High contrast for light-p...

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CA$875.00 - CA$875.00
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CA$447.00 - CA$447.00
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Askar 6nm Colour Magic Super Ha/OIII D1 Filter - 2"

ASK-ASK2DNHOD1
4 in stock

Dual-Bandpass: 8.5nm H-alpha & 6.5nm OIII Peak Transmittance: >85% at 500.7nm and 656.6nm Light Pollution Suppression: ≥OD5 blocking from 2...

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Askar 6nm Colour Magic Super SII/OIII D2 Filter - 2"

ASK-ASK2DNSOD2
3 in stock

Dual-band filter passing OIII (6.5nm) and SII (8.5nm) wavelengths Peak transmittance of 85% for maximum signal capture Designed for color cameras ...

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CA$315.00 - CA$315.00
CA$315.00
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CA$315.00

Askar Colour Magic Ha/OIII & SII/OIII (C1+C2) Filter Package

ASK-CM-C1C2
2 in stock

Complete 2-Filter Narrowband Solution for Color Cameras Captures H-alpha, Oxygen-III, and Sulfur-II Wavelengths Filter 1 (C1): Hα + OIII Duo-Band ...

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CA$167.00 - CA$167.00
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Askar Colour Magic Ha/OIII C1 Filter - 2"

ASK-ASKAR2DBC1
2 in stock

Dual-bandpass filter for H-alpha (656.6nm) and Oxygen-III (500.7nm) Asymmetrical bandwidths: 15nm for H-alpha, 35nm for OIII Greater than 90% peak...

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Askar Colour Magic SII/OIII C2 Filter - 2"

ASK-ASKAR2DBC2
3 in stock

Dual-band filter passing SⅡ (672nm) and OIII (500.7nm) emission lines Designed for one-shot-color cameras to capture data often missed by Hα/OIII ...

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Astrodon H-alpha Filter - 5nm

DON-HA5_31R
Only 1 left!

H-α (hydrogen-alpha) at 656 nm (nanometers) is deep red in color and the most popular narrowband filter. Hydrogen is ubiquitous in the cosmos and i...

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Astrodon SII Filter - 5nm

DON-SII5_31R
Only 1 left!

If you want the look of Hubble Space Telescope (HST) images, such as the famous “Pillars of Creation” (the Eagle Nebula, Messier 16), then the next...

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Baader 3.5/4nm f/2 Ultra-Highspeed Filter Set - CMOS-Optimized H-alpha/O-III/S-II

Options available

3.5nm (H-alpha, S-II) and 4nm (O-III) Bandpasses Optimized for f/2 Ultra-Highspeed Optical Systems CMOS-Optimized with Reflex-Blocker™ Coatings Pr...

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Baader 3.5nm / 4nm Narrowband Filter Set - CMOS-Optimized H-alpha/O-III/S-II

Options available
2 variants in stock

3-Filter Set: H-alpha (3.5nm), O-III (4nm), S-II (3.5nm) Ultra-Narrow Bandpasses for Maximum Image Contrast CMOS-Optimized to Eliminate Halos and ...

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Baader 4nm Ultra-Narrowband OIII Filter - CMOS-Optimized

Options available
2 variants in stock

4nm Ultra-Narrowband OIII Bandpass Optimized for Modern CMOS Sensors Reflex-Blocker™ Hard Coatings to Prevent Halos Life-Coat™ Technology for Extr...

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Baader 6.5nm f/2 Highspeed Filter Set - CMOS-Optimized H-alpha/O-III/S-II

Options available
1 variants in stock

Set of 3 Narrowband Filters: H-alpha, O-III, and S-II 6.5nm Bandpass for high-contrast imaging Optimized for f/2 to f/3.5 High-Speed Optical Syste...

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CA$217.00 - CA$564.00
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Baader 6.5nm H-alpha Filter - CMOS-Optimized

Options available
1 variants in stock

6.5nm FWHM Bandpass CMOS-Optimized Anti-Reflection Coatings Reflex-Blocker™ coatings to prevent halos Life-Coat™ scratch-resistant hard coatings A...

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CA$609.00 - CA$1,589.00
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Baader 6.5nm Narrowband Filter Set - CMOS-Optimized H-alpha/O-III/S-II

Options available
1 variants in stock

6.5nm Narrowband Filter Set for H-alpha, O-III, and S-II Optimized specifically for modern CMOS astronomy cameras Reflex-Blocker™ coatings prevent...

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CA$609.00 - CA$1,589.00
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CA$213.00 - CA$557.00
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CA$213.00

Baader 6.5nm OIII Filter - CMOS-Optimized

Options available
1 variants in stock

6.5nm FWHM Bandpass Optimized for Modern CMOS Sensors Reflex-Blocker™ Hard Coatings Available in 7 Formats (Mounted and Unmounted) Plane-Parallel ...

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CA$213.00 - CA$557.00
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CA$210.00 - CA$552.00
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CA$210.00

Baader 6.5nm SII Filter - CMOS-Optimized

Options available
1 variants in stock

6.5nm FWHM Bandpass Optimized for Modern CMOS Sensors Suppresses Halos and Internal Reflections High-Contrast for Sulfur-II Emission Nebulae Avail...

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CA$124.00 - CA$124.00
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Baader ACF DSLR Astro Conversion Filter - for Canon EOS 300

BAA-2459211

Designed for Canon EOS 300 DSLR Astro-Conversion Dramatically Improved Spectral Transmission for Astrophotography Unlocks Critical Hydrogen-Alpha ...

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CA$139.00 - CA$139.00
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Baader ACF DSLR Astro Conversion Filter - for Canon EOS 350D/10D/20D/30D

BAA-2459212

Designed for Canon EOS 350D, 10D, 20D, and 30D DSLRs Improves Spectral Transmission for Astrophotography Unlocks Sensitivity to Hydrogen-Alpha (Hα...

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Baader BCF DSLR Astro Conversion Filter - for Canon EOS

BAA-2459213
1 in stock

Replaces stock DSLR filter to dramatically increase H-alpha sensitivity Enables detailed imaging of emission nebulae Designed for a wide range of ...

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CA$116.00

Baader C2 Swan-Band Comet Filter (15nm)

Options available
2 variants in stock

Targets C2 Swan Bands in comet gas tails 15nm bandpass for high-contrast views O-III parallel transmission for nebula observation Available in 1.2...

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CA$63.00

Baader Clear Focusing Filter

Options available
1 variants in stock

Enables precise focusing for dim narrowband filters Perfectly parfocal with other Baader Planetarium filters Optically polished to ensure no image...

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CA$63.00 - CA$152.00
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CA$63.00

Filter Types and When Each One Earns Its Place

Filters do not add signal. They remove unwanted light so that the signal you want has better contrast against the background. Choosing well means knowing which unwanted light you are fighting.

  • Narrowband filters: Ha, OIII and SII passbands, typically 3 to 12 nm. Narrower bands reject more light pollution and moonlight but demand accurate focus and longer exposures.
  • LRGB filter sets: Parfocal luminance, red, green and blue for colour imaging with monochrome sensors, with the luminance channel carrying most of the detail.
  • Light pollution filters: Broadband rejection of mercury and sodium emission lines. Effective against older street lighting and much less effective against broad-spectrum LED.
  • Planetary and colour filters: Wratten-standard colour filters that raise contrast on specific planetary features — a red or orange filter on Mars, blue on Jupiter's belts.
  • Solar filters: Full-aperture white-light filters for safe observation of sunspots and transits.
  • Neutral density and polarizing: Variable brightness reduction for lunar observing without altering colour balance.

Why Choose David Astro for Filters

A filter that performs beautifully at f/7 can produce a shifted passband and soft results at f/3. That is the kind of detail worth asking about before ordering.

  • F-ratio matched recommendations: Narrowband passbands shift blueward in fast optical systems, so we recommend filters specified for your focal ratio rather than the narrowest available.
  • Sensor size and vignetting: We size filters to your sensor diagonal and filter wheel placement, so an undersized filter does not clip your corners.
  • Spacing accounted for: Filter glass shifts focus by roughly a third of its thickness, and we include that in the back-focus calculation we provide.
  • Authorized dealer: Genuine filters with full manufacturer warranty and verified coatings, in Canadian inventory and shipped domestically.
  • Ships from Canada: No duties or brokerage charges for Canadian buyers.

Filters in Canada — Frequently Asked Questions

Do light pollution filters still work under LED streetlights?
Much less well than they did under sodium lighting. LED emits across a broad spectrum, so there is no narrow band to reject. Narrowband filters remain effective because they pass only emission lines regardless of what the streetlight does.
How narrow should my Ha filter be?
For f/5 and slower, 3 to 5 nm gives excellent contrast. Below about f/4, the incident light cone shifts the passband and a 6 to 7 nm filter, or one specified for fast optics, performs better.
What size filters do I need?
Match the sensor diagonal plus the distance from filter to sensor. A 36 mm filter typically covers APS-C in a standard wheel; full frame usually needs 50 mm square or unmounted 2 inch.
Are filters shipped from Canada?
Yes, in-stock filters are held in our Canadian warehouse and reach Canadian customers without customs handling.

Building a filter set?

Tell us your telescope, camera and sky conditions and we will recommend the right bandwidths and sizes. Canadian stock, fast domestic shipping.