ZWO Hydrogen-Alpha Ha Filter - 31mm
Best narrowband filter for deep sky astrophotography.
Enhance your astrophotography with this specialized narrowband filter, designed to significantly boost contrast between nebulae and the night sky. It effectively minimizes light pollution from artificial sources and natural skyglow, allowing intricate details of celestial objects to emerge. The filter precisely passes light at the 656nm wavelength with a narrow 7nm bandpass, achieving up to 90% transmission. Its optically polished glass ensures superior performance, making it ideal for capturing stunning images even in challenging light conditions. This unmounted filter is designed for seamless integration with drop-in filter holders.
$149.00
More H-alpha Filter Options
Owner Satisfaction
4.6
/ 5
Category Rank
398
/ 1292
#398 in Lens Filters
Price vs Category Average
-22%
Below average
FWHM
70.5
/ ±nm
Who it's for
- Astrophotographers focused on detailed emission nebulae
- Urban astrophotographers needing to overcome bright skies
- Imagers prioritizing high-contrast, sharp nebulae features
Who should skip it
- Newcomers expecting immediate full-color astrophotography results
- Imagers with limited patience or less precise tracking setups
- Astrophotographers seeking a single, versatile filter solution
Key Specs
FWHM
7±0.5nm
Glass Thickness
2.0+/-0.03 mm
Transmission
90% at H-alpha line 656nm
Filter Shape
Round
Filter Insert Style
Drop-In
Optical Density
OD3
Warranty
2 Years
Filter Diameter
31mm
Know before you buy
A 7nm bandpass is narrow enough to isolate the specific light emitted by hydrogen-alpha regions while blocking out most artificial light pollution and natural skyglow. This allows you to capture high-contrast images of nebulae even when shooting from light-polluted urban or suburban environments.
Yes. Because this filter only allows a very specific wavelength of light to pass through, it effectively suppresses the broad-spectrum light from the moon, allowing you to continue imaging nebulae even during brighter moonlit nights.
This is an unmounted 31mm round filter. It is specifically designed for use in filter wheels or drop-in filter holders rather than for threading directly onto a camera lens.
No, this is a narrowband filter designed specifically for emission nebulae that glow at the 656nm hydrogen-alpha wavelength. It will not be effective for broadband targets like galaxies, reflection nebulae, or star clusters.
Standard light pollution filters are typically broadband and only block specific wavelengths of streetlights. This H-alpha filter is much more aggressive, blocking almost all light except for the narrow 656nm band, which provides significantly higher contrast for nebulae but requires longer exposure times.
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