ZWO 31mm H-alpha Filter - 7nm
Best narrow-band filter for deep-sky nebula astrophotography enthusiasts.
Capture the intricate beauty of emission nebulae with this specialized filter. It precisely isolates the Hydrogen Alpha wavelength at 656nm, utilizing a narrow 7nm bandwidth to significantly boost contrast against the night sky. This enhances the visibility of faint celestial objects and improves overall image clarity for deep-sky astrophotography. Its 31mm size ensures compatibility with a wide range of telescope setups, making it an essential tool for enthusiasts seeking to reveal the cosmos in greater detail and definition.
$149.00
More Narrowband Filter Options
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ZWO 31mm Ha 7nm Narrowband Unmounted Filter
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ZWO 1.25" Narrowband Filter Set
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Owner Satisfaction
4.6
/ 5
Category Rank
1569
/ 2593
#1569 in Telescope Accessories
Price vs Category Average
-78%
Below average
Bandpass
7
/ nm
Who it's for
- Urban astrophotographers battling heavy light pollution
- Deep-sky imagers focusing on emission nebulae detail
- Serious hobbyists demanding high-transmission optical performance
Who should skip it
- Impatient imagers lacking time for long-exposure integration
- Generalists seeking a versatile filter for galaxies and clusters
- Budget-conscious beginners without monochrome camera systems
Performance breakdown
Nebula Contrast
Narrow 7nm bandwidth effectively isolates emission lines for striking deep-sky results.
Light Pollution Suppression
Blocks unwanted artificial light to reveal faint structures in urban skies.
Optical Precision
Maintains high transmission at 656nm for sharp, clear celestial imaging.
Build Quality
Durable construction ensures long-term reliability for demanding astrophotography sessions.
Compatibility
Standard 31mm sizing integrates seamlessly with most popular filter wheels.
Imaging Versatility
Specialized for H-alpha, though limited to monochromatic deep-sky capture workflows.
Key Specs
Bandpass
7nm
Filter Type
H Alpha
Size
31mm
Wavelength
656nm
Model Number
ZWO-HA7-31MM
Material
Glass
Mounting Type
Screw-in
Accessory Type
Filter
Know before you buy
A 7nm bandwidth is narrow enough to effectively block light pollution and moonlight, which significantly increases the contrast of emission nebulae. By isolating the specific 656nm wavelength, it allows you to capture faint details that would otherwise be washed out by background sky glow.
The 31mm size is an unmounted filter typically designed for use in electronic filter wheels. You should verify that your filter wheel or camera adapter is compatible with 31mm unmounted optics before purchasing.
This filter is specifically optimized for deep-sky astrophotography. While it can technically be used visually, the narrow 7nm bandpass will make the view extremely dim, and it is not recommended for standard eyepiece observation.
If you are shooting in monochrome, you will typically pair this with OIII and SII filters to create a 'Hubble Palette' (SHO) image. If you are using a color camera, this filter will only capture data on the red channel, which is useful for monochrome-style detail but not for standard full-color imaging.
This filter is highly effective in light-polluted environments because it ignores most artificial light sources. It allows you to continue imaging even when the moon is bright or you are located near city lights, provided you are targeting emission nebulae.
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$149