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
Antlia 3nm Narrowband H-alpha Pro Filter
Isolates the H-alpha emission line at 656.3nm 3nm bandpass (FWHM) to enhance contrast of emission targets Peak transmission greater than 88% Guara...
View full detailsAntlia 3nm Narrowband H-alpha Pro Highspeed Filter - f/2.6 to f/3.6
Optimized for fast optical systems from f/2.6 to f/3.6 3nm bandpass (FWHM) around the H-alpha line Center wavelength pre-shifted 1.2nm to the red ...
View full detailsAntlia 3nm Narrowband H-Beta Pro Filter - 2"
Isolates the H-Beta emission line at 486.1nm 3nm bandpass (FWHM) to enhance contrast of emission targets 88% peak transmission Greater than OD5 bl...
View full detailsAntlia 3nm Narrowband NII Pro Filter - 2"
Isolates the Nitrogen-II (NII) emission line at 654.8nm 3nm bandpass (FWHM) 88% peak transmission Greater than OD5 out-of-band blocking from 300-1...
View full detailsAntlia 3nm Narrowband OIII Pro Filter
5.0 / 5.0
2 Reviews
3nm FWHM (Full Width at Half Maximum) Centered on the 500.7nm OIII emission line Peak transmission greater than 88% Out-of-band blocking >OD5 (...
View full detailsAntlia 3nm Narrowband OIII Pro Highspeed Filter - f/2.6 to f/3.6
Optimized for f/2.6 to f/3.6 optical systems 3nm FWHM (Full Width at Half Maximum) Center wavelength pre-shifted 1.2nm to the red (501.9nm) Peak T...
View full detailsAntlia 3nm Narrowband SII Pro Filter
5.0 / 5.0
1 Review
Isolates the Sulfur-II emission line at 672.4nm 3nm bandpass (FWHM) to enhance contrast of emission targets Peak transmission greater than 88% Usa...
View full detailsAntlia 3nm Narrowband SII Pro Highspeed Filter - f/2.6 to f/3.6
Optimized for fast optical systems from f/2.6 to f/3.6 Central wavelength pre-shifted by 1.2nm to 673.6nm to compensate for blue shift 3nm bandwid...
View full detailsAntlia 4.5nm Narrowband H-alpha Edge Filter
4.5nm Narrowband H-alpha Filter Usable down to f/3 with minimal loss of signal Peak transmission greater than 90% at 656.3nm Out-of-band blocking ...
View full detailsAntlia 4.5nm Narrowband OIII Edge Filter
4.5nm FWHM Narrowband OIII Filter Centered on the 500.7nm OIII Emission Line Peak Transmission >85% Out-of-Band Blocking >OD5 (0.001%) from ...
View full detailsAntlia 4.5nm Narrowband SII Edge Filter
Captures ionized sulfur emissions at a central wavelength (CWL) of 672.4nm Tight 4.5nm FWHM bandpass isolates faint nebulae from background skyglo...
View full detailsAntlia 7nm Narrowband H-alpha Prime Filter
7nm Full Width at Half Maximum (FWHM) Bandpass Centered on the 656.3nm Hydrogen-alpha Emission Line Passes NII Emission Lines at 654.8nm and 658.3...
View full detailsAntlia 7nm Narrowband OIII Prime Filter
Isolates the 500.7nm OIII emission line 7nm FWHM bandpass for high signal capture Greater than 90% peak transmission OD4 (0.01%) out-of-band block...
View full detailsAntlia 7nm Narrowband SII Prime Filter
Captures Sulfur-II emission lines at a central wavelength (CWL) of 672.4nm 7nm FWHM bandpass passes the SII lines at 671.6nm and 673.1nm Greater t...
View full detailsAntlia 8-EL UHC Pro Visual Enhanced Filter - 2"
Enhances 8 key nebular emission lines for visual use Peak transmission of 95% at H-beta, OIII, NII, H-alpha, and SII wavelengths Recommended for l...
View full detailsAntlia ALP-T Dual Band Ha&OIII 3nm
5.0 / 5.0
1 Review
Passes H-alpha (656.3nm) and OIII (500.7nm) emission lines 3nm (+0.6/-0.1nm) FWHM on both lines Peak transmission of 90% (H-alpha) and 82% (OIII) ...
View full detailsAntlia ALP-T Dual Band Ha&OIII 3nm + SII&Hb 3.5nm 2" Filter Set
Two dual-band filters for four narrowband channels with color cameras; also usable with mono cameras Ha & OIII Filter: 3nm FWHM at 656.3nm and...
View full detailsAntlia ALP-T Dual Band SII&Hβ 3.5nm
Dual-band filter passing Sulfur-II (672.4nm) and Hydrogen-beta (486.1nm) 3.5nm (+/-0.5nm) FWHM on both lines Peak transmission of 90% (SII) and 85...
View full detailsAntlia ALP-T Dualband 5nm Ha/OIII and SII/Hb Filter Set - 2"
2-filter set captures four narrowband channels (Ha, OIII, SII, H-beta) with one-shot color cameras Ha/OIII filter isolates H-alpha (656.3nm) and O...
View full detailsAntlia ALP-T Dualband 5nm Ha/OIII Filter
Dual line-pass filter for Hydrogen-alpha (656.3nm) and Oxygen III (500.7nm) Tight 5nm FWHM bandpass for both emission lines Peak transmission of 9...
View full detailsAntlia ALP-T Dualband 5nm Ha/OIII Highspeed Filter
Dual 5nm bandpasses for Hydrogen-alpha (657.8nm) and Oxygen-III (502.2nm) Optimized for high-speed imaging systems from f/2.2 to f/3.6 Peak transm...
View full detailsAntlia ALP-T Dualband 5nm SII/Hb Filter
Dual-bandpass 5nm design for one-shot color (OSC) cameras Passes Sulfur-II (672.4nm) and Hydrogen-Beta (486.1nm) emission lines Peak transmission ...
View full detailsAntlia CH4 Methane Filter - 1.25"
Isolates the 889nm methane absorption band for planetary imaging 20nm wide bandpass centered at 889nm, in the near infrared Average transmission a...
View full detailsAntlia H-alpha 2.5nm Ultra Narrowband Filter
Isolates the H-alpha emission line at 656.3nm Ultra-narrow 2.5nm FWHM bandpass to maximize contrast Peak transmission of >=95% Deep >=OD5 (0...
View full detailsFilter 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.